Choosing the right strategy · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Choosing the right strategy

Mathematics · Mathematical Thinking · ages 7-8
Name ______________________   Date ____________

  1. What is 345 + 200?

    Answer: ______________

  2. Which is the best way to work out 345 + 200?

    • Add 2 to the hundreds digit in your head
    • Draw hundreds of little sticks and count them all
    • Weigh the numbers on a scale
    • Measure the numbers with a ruler

  3. Which is quickest to solve in your head: 200 + 300, or 268 + 347?

    • 200 + 300
    • 268 + 347
    • They are the same

  4. A number line can help you add numbers by hopping along it.

    Circle one:   True   False

  5. What is 345 + 278?

    Answer: ______________

  6. Use hops on a number line to solve 24 + 9. What is the answer?

    2022242628303335+9

    Answer: ______________

  7. Which tool should you use to measure a pencil?

    • A metre stick
    • A ruler
    • A bathroom scale
    • A measuring jug

  8. Dan says 345 + 278 is easy to do mentally because no regrouping is needed. Is Dan right?

    Circle one:   True   False

  9. Tom is adding 3999 + 2. Which is the smartest way to solve it?

    • Think it through in his head, since 3999 is close to 4000
    • Write it out with long addition
    • Draw base-ten blocks for 3999

  10. A number line shows jumps of 10 starting from 345. After 3 jumps, which number is reached?

    Answer: ______________

LightMySky · lightmysky.comW1-mt_mQcWGh02no-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

Choosing the right strategy W1-mt_mQcWGh02no-s1

  1. 545 · Only the hundreds digit changes: 3 hundreds plus 2 hundreds is 5 hundreds, so 545.
  2. Add 2 to the hundreds digit in your head · Adding 200 only changes the hundreds digit, so it is quick and safe to do mentally.
  3. 200 + 300 · 200 + 300 uses round numbers, so you can add them in your head fast.
  4. True · Hopping forward on a number line is one good way to add.
  5. 623 · Column addition with regrouping: ones 5 + 8 = 13, tens 4 + 7 + 1 = 12, hundreds 3 + 2 + 1 = 6, so 623.
  6. 33 · Hop from 24 forward 9 steps and you land on 33.
  7. A ruler · A pencil is centimetres long, so a ruler is the tool that fits.
  8. False · Dan is wrong. The ones (5 + 8) and the tens (4 + 7) both regroup, so a written method is the safer choice.
  9. Think it through in his head, since 3999 is close to 4000 · 3999 is nearly 4000, so thinking 4000 + 2 - 1 in his head beats writing it all out.
  10. 375 · Three jumps of 10 make 30, and 345 + 30 = 375.
Worksheet · LightMySky