Number Line ×
1
Line
Numbers
Custom line from to Whole numbers from −1000 to 1000, including 0, between 5 and 200 apart.
Number of steps
4
Size of each step
3
Swap
Signs
Missing
Step sizes (tables) On the tenths lines the steps are 0.1 to 1.9
History

Investigation questions

62 questions. Use these with the number line above. Set it up loads the calculation (your own work is one undo away), and Show on board puts the question on screen, full size. Keep 🙈 Predict on so the class commits to an answer before it is revealed.

↑ Back to the tool

First experiments
5 questions
  1. The line shows 4 × 3. Before you start, say where you will land. Press Go once for each step, then once more (or click 👁) to reveal the answer. Which way does the arrow under 0 point, and why?

    Teacher notes

    12, after four teal steps of +3 landing on 3, 6, 9 and 12. The arrow points right because 3 is positive. With 🙈 Predict on, the answer waits for a fifth press, so ask for a prediction every time.

  2. Tap the line at 5. What happens to the calculation, and why? Now tap the line at −2.

    Teacher notes

    Tapping sets the size of each step. 4 × 5 = 20 is off the line, so the tool cuts the steps to 2 × 5 = 10 and says so. Tapping −2 gives 2 × (−2) = −4, with the arrow now pointing left.

  3. Type 7 × 8 in the box and press Set. Which line does the tool choose, and why? Now type (−3) × (−4). Does the line change?

    Teacher notes

    56 needs 0 to 100 (0 to 24 and 0 to 48 are too short). (−3) × (−4) = 12 stays on 0 to 100: you face left of 0 but walk backwards, so every stop (4, 8, 12) is positive.

  4. Turn on ➕ Repeated addition and step through 4 × 3 with Go. What does the tool write, and what happens to it after each step?

    Teacher notes

    “4 lots of 3: 3 + 3 + 3 + 3”, with one 3 turning dark as each step lands, and “= 12” when the answer is revealed. The first number counts how many 3s are added.

  5. Switch to Compare, Practice and Missing number in turn (or press 2, 3 and 4), then go back to Explore. Is your calculation still there?

    Teacher notes

    Yes: each mode keeps its own work and undo. 🗑 (tapped twice) starts just one mode again, and undo (U) brings it back.

Steps and times tables
5 questions
  1. Start with 1 × 5. Press ▲ under Number of steps to make 2 × 5, 3 × 5 and 4 × 5, watching each one. What stays the same and what changes? Where will 8 × 5 land?

    Teacher notes

    5, 10, 15, 20: the step stays 5 and there is one more step each time, so the answer goes up by 5. 8 × 5 = 40. The first number counts the steps.

  2. Now keep 3 steps and change the step size: 3 × 1, 3 × 2, 3 × 3, 3 × 4. How much does the answer go up each time? Why?

    Teacher notes

    3, 6, 9, 12: up by 3 each time, because each of the 3 steps gets 1 longer. Compare with the last question, where the answer went up by the step size.

  3. Turn on 🔢 Multiples with 3 × 4 on 0 to 24. Which numbers are ringed? Without pressing Go, say where 5 × 4 will land, then check.

    Teacher notes

    4, 8, 12, 16, 20 and 24: the 4 times table. Every step lands on a ring, and 5 × 4 = 20 is the fifth ring from 0.

  4. On 0 to 24 with 6 steps, how big can each step be before the ▲ stops working? What about 4 steps? 5 steps?

    Teacher notes

    4 (6 × 4 = 24), 6 (4 × 6 = 24) and 4 (5 × 4 = 20, as 5 × 5 = 25 is off the line). The arrows stop when the answer would leave the line, which is the biggest multiple that fits.

  5. Set Numbers to None and watch 3 × 7 on 0 to 24. Which numbers still appear? How does this help you count in 7s?

    Teacher notes

    0, 7, 14 and 21: the start, each stop and the answer are always labelled. On an empty line the labels are exactly the multiples of 7 you pass.

Swapping the numbers
4 questions
  1. Watch 4 × 3, then press ⇄ and watch 3 × 4. Same answer? Same journey?

    Teacher notes

    Both give 12, but 4 × 3 is four steps of 3 and 3 × 4 is three steps of 4. The answers always match (multiplication is commutative) even though the journeys don’t.

  2. The line shows 9 × 2 with ➕ Repeated addition on. Press ⇄ to get 2 × 9. Which is quicker to work out?

    Teacher notes

    Both are 18: nine 2s, or two 9s (9 + 9). Choosing the order with fewer steps is a useful mental strategy.

  3. Press ⇄ on (−2) × 5. Do the two journeys land in the same place? Describe how each one gets there.

    Teacher notes

    Both land on −10. (−2) × 5 faces right and walks backwards 2 steps of 5; 5 × (−2) faces left and walks forwards 5 steps of 2.

  4. Compare 1 × 7 and 7 × 1 on 0 to 24. What do you notice about multiplying by 1?

    Teacher notes

    Both are 7: one step of 7, or seven steps of 1. Multiplying by 1 leaves a number unchanged.

Steps of a negative size
5 questions
  1. The line shows 3 × (−4). Which way does the arrow under 0 point? Predict where you will land, then press Go until it is revealed.

    Teacher notes

    −12. The arrow points left because −4 is negative, and you walk forwards 3 steps of 4, so all three steps are amber, landing on −4, −8 and −12.

  2. Watch 3 × 4, then press ▼ under Size of each step until you reach 3 × (−4), watching each one. What happens to the answer as the step size goes down by 1?

    Teacher notes

    12, 9, 6, 3, 0, −3, −6, −9, −12: down by 3 each time. The pattern carries on past 0, which is why 3 × (−4) = −12, the mirror image of 3 × 4 in 0.

  3. Turn on ➕ Repeated addition for 4 × (−3). What sum does the tool write?

    Teacher notes

    “4 lots of (−3): (−3) + (−3) + (−3) + (−3) = −12”. Adding negative numbers moves further left each time.

  4. Predict 2 × (−6), 3 × (−4), 4 × (−3) and 6 × (−2), then check each one.

    Teacher notes

    All four are −12, made from the factor pairs of 12 with a negative step. The more steps there are, the shorter each one is.

  5. On −24 to 24, steps of −5: how many steps can you take before the arrow stops? Where do you land?

    Teacher notes

    4 steps, landing on −20; a fifth would reach −25, which is off the line. On the positive side, 4 × 5 = 20 is also the limit.

A negative number of steps
5 questions
  1. The line shows (−2) × 3. Which way do you face? Which way do you walk? Predict where you land.

    Teacher notes

    −6. You face right (3 is positive) and walk backwards 2 steps, so you move left. The facing arrow is teal but the steps are amber: the colours show facing and moving separately.

  2. Turn on ➕ Repeated addition for (−3) × 4. What does the tool write? Why does it start with 0?

    Teacher notes

    “Take away 3 lots of 4: 0 − 4 − 4 − 4 = −12”. A negative number of steps takes groups away, starting from 0.

  3. Watch 3 × 2, then press ◀ under Number of steps (or the ← key) one at a time until you reach (−3) × 2. Write down every answer.

    Teacher notes

    6, 4, 2, 0, −2, −4, −6: down by 2 each time. 0 × 2 = 0 (no steps), and the pattern continues below zero, so (−1) × 2 = −2.

  4. Try (−1) × 7, then (−1) × 5 and (−1) × (−8). What does multiplying by −1 do?

    Teacher notes

    −7, −5 and 8. One step backwards lands on the opposite number, the same distance from 0 on the other side.

  5. Using a negative number of steps and positive step sizes, how many ways can you land on exactly −10 on −12 to 12?

    Teacher notes

    Four: (−1) × 10, (−2) × 5, (−5) × 2 and (−10) × 1, one for each factor pair of 10.

Negative × negative
6 questions
  1. The line shows (−2) × (−3). Use the walking method to predict: which way do you face, which way do you walk, and where do you land?

    Teacher notes

    6. Face left (−3 is negative), walk backwards 2 steps, so you move right: the arrow is amber and the steps are teal. Facing left and walking backwards is the whole reason (−) × (−) is positive.

  2. Find 3 × 2, (−3) × 2, 3 × (−2) and (−3) × (−2). Which are positive, and which are negative?

    Teacher notes

    6, −6, −6 and 6. The answer is positive when the signs match and negative when they differ; the size is always 6.

  3. Turn on ➕ Repeated addition for (−3) × (−4). What does it write? How does this link to subtracting negative numbers?

    Teacher notes

    “Take away 3 lots of (−4): 0 − (−4) − (−4) − (−4) = 12”. Subtracting −4 moves 4 to the right, so taking away three of them lands on 12.

  4. Watch (−3) × 3, then press ▼ under Size of each step until you reach (−3) × (−3), watching each one. What pattern do the answers make?

    Teacher notes

    −9, −6, −3, 0, 3, 6, 9: up by 3 each time the step size drops by 1. Keeping the pattern going past 0 gives (−3) × (−1) = 3 without any walking.

  5. Find (−1) × (−1), (−2) × (−2) and (−3) × (−3). Will (−4) × (−4) fit on −12 to 12? Can a number times itself ever be negative?

    Teacher notes

    1, 4 and 9. (−4) × (−4) = 16 needs −24 to 24. A number times itself is never negative: matching signs always give a positive answer.

  6. Switch to 0 to 24 and type (−4) × (−6). Does it fit? Watch it: where are the stops?

    Teacher notes

    Yes, 24. The arrow points left of 0, but walking backwards takes you right, so the stops are 6, 12, 18 and 24, all on a line with no negative numbers.

Zero
4 questions
  1. The line shows 5 × 0. Predict the answer, then watch.

    Teacher notes

    0. Five hops on the spot: a step of 0 goes nowhere, however many you take. Pupils who say 5 often think “times 0 does nothing”.

  2. Now try 0 × 7. How is the journey different from 7 × 0?

    Teacher notes

    Both are 0. 0 × 7 faces right but takes no steps; 7 × 0 takes seven steps that go nowhere.

  3. Watch 4 × 3, then press ▼ under Size of each step to make 4 × 2, 4 × 1, 4 × 0 and 4 × (−1). What pattern do the answers make?

    Teacher notes

    12, 8, 4, 0, −4: down by 4 each time. 4 × 0 = 0 sits exactly where the pattern says it should.

  4. Can you land on 0 without using 0 in the calculation? Try to find one, then explain.

    Teacher notes

    No. If neither number is 0, you take at least one step of a size other than 0, and every step moves you the same way, so you can never come back to 0.

Missing numbers: division
6 questions
  1. The line shows □ × 3 = 12. How many steps of 3 does it take to reach 12? Predict, then press Go to count them.

    Teacher notes

    4, so 12 ÷ 3 = 4. This is division as grouping: how many 3s fit into 12. The steps are numbered as they land.

  2. Now the line shows 4 × □ = 12. Four equal steps reach 12. How big is each one?

    Teacher notes

    3, so 12 ÷ 4 = 3. This is division as sharing: 12 split into 4 equal parts. The same fact, 4 × 3 = 12, gives both divisions.

  3. The line shows □ × 4 = 24. Predict the missing number, then count the steps.

    Teacher notes

    6, as 24 ÷ 4 = 6. Pupils who answer 20 are subtracting instead of dividing.

  4. On −12 to 12 the line shows □ × 3 = −12. You face right, but −12 is to the left. How many steps, and which way do you walk?

    Teacher notes

    −4: walk backwards 4 steps. So (−12) ÷ 3 = −4: dividing a negative number by a positive one gives a negative answer.

  5. The line shows (−2) × □ = 12. You walk backwards 2 steps and land on 12, to the right. Which way must you be facing? How big is each step?

    Teacher notes

    −6: you must face left, so each step is −6. So 12 ÷ (−2) = −6.

  6. With only How many steps chosen, press New question five times. Before pressing Go, write each one as a division and predict the answer.

    Teacher notes

    □ × 3 = −12 is (−12) ÷ 3, and so on. The missing number is positive when the answer and the step size have the same sign, and negative when they differ, the same rule as multiplying.

Comparing two lines
4 questions
  1. Line A is 4 × 3 and line B is 3 × 4. Press ▶ Both (then reveal each answer). What does the tool say about where they land?

    Teacher notes

    “A and B land in the same place”: both 12, with a purple line joining them. A takes four steps of 3, B three steps of 4.

  2. Line A is 3 × (−4) and line B is (−3) × 4. Predict first: same answer? Same direction of facing? Then press ▶ Both.

    Teacher notes

    Both −12, but A faces left and walks forwards while B faces right and walks backwards. Two different journeys, one destination.

  3. Line A is 2 × 6 and line B is (−2) × (−6). How are the two journeys alike, and how are they different?

    Teacher notes

    Both are two teal steps of 6 to the right, landing on 12. A faces right and walks forwards; B faces left and walks backwards.

  4. Line A is 5 × 2 and line B is 5 × (−2). How far apart do they land?

    Teacher notes

    20: the tool says “A lands 20 to the right of B” (10 and −10). Changing the sign of one number reflects the answer in 0.

Practice
4 questions
  1. In Practice on 0 to 24 with only (+) × (+), press New question ten times. Can the answer be more than 24? Can it be 0?

    Teacher notes

    Neither. Questions use 2 to 10 steps and step sizes from the chosen tables, and always fit the line, so the answers run from 4 to 24.

  2. Choose only the 7 under Step sizes (tables) on 0 to 100. What is the biggest answer a question can have? The smallest?

    Teacher notes

    70 (10 × 7) and 14 (2 × 7). Choosing one table turns Practice into skip-counting practice for that table.

  3. On −24 to 24 with all four signs, make 20 questions and tally how many answers are positive. Is it about half?

    Teacher notes

    Expect about 10, usually between 6 and 14. Each sign type is equally likely and two of the four give a positive answer; 0 never appears because both numbers are at least 2 in size.

  4. Choose only (−) × (+) on −12 to 12, then press 🖨 and choose Six questions, with answers. Try the sheet without the tool, then check with the answer page.

    Teacher notes

    The sheet uses the signs and tables chosen in Practice, and the answer page draws every step. Every answer is negative: facing right and walking backwards.

Decimals
5 questions
  1. On 0 to 2 in tenths the line shows 3 × 0.4. Predict, then watch.

    Teacher notes

    1.2, landing on 0.4, 0.8 and 1.2. Pupils who write 0.12 are treating it like 0.3 × 0.4; the line shows three steps of four tenths, which is twelve tenths.

  2. Press ⇄ on 3 × 0.4. What does the tool say? Is 0.4 × 3 still 1.2?

    Teacher notes

    It refuses: you can’t take 0.4 steps. 0.4 × 3 is still 1.2, but it means 0.4 of 3, a scaling, which the walking model can’t show. A good moment to discuss the limits of a model.

  3. Find 5 × 0.2, then 2 × 0.5, then 10 × 0.1. What do you notice?

    Teacher notes

    All three are 1: five fifths, two halves and ten tenths of 1.

  4. On −2 to 2 in tenths, predict (−3) × 0.6, then check.

    Teacher notes

    −1.8: face right and walk backwards 3 steps of 0.6. The sign rules are the same for decimals.

  5. In Missing number, the line shows 4 × □ = 2. How big is each step?

    Teacher notes

    0.5, so 2 ÷ 4 = 0.5. Sharing a whole number into more parts than its size gives a step smaller than 1.

Predictions and misconceptions
4 questions
  1. A pupil says multiplying always makes a number bigger. Test 4 × 1, 4 × 0 and 4 × (−2). Is the pupil right?

    Teacher notes

    4, 0 and −8, so no. Multiplying by 1 changes nothing, by 0 gives 0, and by a negative number gives something smaller. On the tenths lines, 4 × 0.5 = 2 is smaller too.

  2. A pupil says 3 × (−2) = 6 because “two negatives make a positive”. Turn on ➕ Repeated addition and check.

    Teacher notes

    −6: (−2) + (−2) + (−2). There is only one negative number here, and adding negatives makes the answer more negative.

  3. A pupil says 5 × 3 is 8. Turn on ➕ Repeated addition and watch. What has the pupil done?

    Teacher notes

    15: five 3s, 3 + 3 + 3 + 3 + 3. The pupil added 5 and 3; the first number counts the steps rather than being added on.

  4. A pupil says (−4) × 3 = 12, “because you just multiply the numbers”. Predict with the walking method, then check.

    Teacher notes

    −12. The size is 12, but walking backwards while facing right moves left. Ask pupils to find the sign first, then the size.

Open investigations
5 questions
  1. How many different multiplications land on exactly 12 on −12 to 12, without using 0? How many land on −12?

    Teacher notes

    12 each. For 12: 1 × 12, 2 × 6, 3 × 4, 4 × 3, 6 × 2, 12 × 1 and the same six with both numbers negative. For −12, one of each pair is negative, which also gives 12.

  2. Find a multiplication where the number of steps, the step size and the answer are all the same number. How many can you find?

    Teacher notes

    Two: 1 × 1 = 1 and 0 × 0 = 0. (−1) × (−1) = 1 doesn’t count, as the answer is not −1.

  3. Start with 3 × 4. Double the number of steps: what happens to the answer? Now double both numbers instead.

    Teacher notes

    6 × 4 = 24 doubles the answer; 6 × 8 = 48 makes it four times as big, because each doubling doubles the answer.

  4. In Compare, make two journeys that look as different as possible but land in the same place. What makes them look so different?

    Teacher notes

    For example 12 × 1 (twelve small steps right) and (−1) × (−12) (one long step backwards). Different numbers of steps, sizes and directions of facing can all give the same answer.

  5. Design your own investigation. Choose a mode, a line and the settings, then press 🔗 to copy a link so a partner opens the tool exactly as you set it up.

    Teacher notes

    The link stores the mode, the line, the calculation, the settings and how far it has played, but not the undo history. Good questions ask for a prediction first and say which settings to use.