Using a Calculator Well · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Using a Calculator Well

Mathematics · Mathematical Thinking · ages 11-14
Name ______________________   Date ____________

  1. Key (6 + 4) x 5 correctly. What should the display show?

    Answer: ______________

  2. You want 5 lots of a 10-pound bundle made from 6 pounds plus 4 pounds. Which calculator keying gives the right total?

    • 6 + 4 x 5
    • 6 + (4 x 5)
    • (6 + 4) x 5
    • 5 x 6 + 4

  3. You want to work out (5 + 3) × 2 on a calculator. Which keys give the right answer?

    • 5 + 3 × 2
    • ( 5 + 3 ) × 2
    • 5 + ( 3 × 2 )

  4. Before typing numbers into a calculator, it helps to guess roughly what the answer should be.

    Circle one:   True   False

  5. A calculator shows 3.5 hours for a film. How many minutes is that?

    Answer: ______________

  6. Jamal estimates an answer should be about 40. His calculator shows 400. What should he do?

    • Trust the calculator, it's always right
    • Check his keying for a mistake like a missing bracket or an extra digit
    • Round 400 down to 40

  7. A calculator shows 4.5 for a bill in pounds. How should you read it?

    • 4 pounds 50p
    • 4 pounds 5p
    • 45 pounds
    • 4 pounds and a half p

  8. Dan keys 6 + 4 x 5 without brackets, gets 26, but wanted (6 + 4) x 5 = 50. He says brackets were needed. Is Dan right?

    Circle one:   True   False

  9. Aisha wants to work out (6 + 2) ÷ 4, which should give 2. She keys 6 + 2 ÷ 4 without brackets. What does the display show instead?

    • 8
    • 2
    • 6.5

  10. A display shows 2.75 hours. How long is that in hours and minutes?

    • 2 hours 75 minutes
    • 2 hours 7 minutes
    • 3 hours 15 minutes
    • 2 hours 45 minutes
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Answer key

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

Using a Calculator Well W1-mt_FZE80D2jS_-s1

  1. 50 · Brackets first: 10, then x 5 = 50.
  2. (6 + 4) x 5 · Only brackets force the addition first: (6 + 4) x 5 = 10 x 5 = 50.
  3. ( 5 + 3 ) × 2 · The brackets force the calculator to add 5 and 3 first, then multiply the result by 2.
  4. True · A rough guess gives you something to compare the display against, so you can catch keying mistakes.
  5. 210 · 3 hours plus 0.5 x 60: 180 + 30 = 210 minutes.
  6. Check his keying for a mistake like a missing bracket or an extra digit · A calculator only follows the keys you press, so a big gap from your estimate usually means a keying mistake.
  7. 4 pounds 50p · Half a pound is 50 pence, so 4.5 pounds is 4 pounds 50p.
  8. True · Dan is right: order rules multiply first (26); only brackets force 50.
  9. 6.5 · Without brackets the calculator divides 2 by 4 first (0.5), then adds 6, giving 6.5. She needed (6 + 2) ÷ 4 to get 2.
  10. 2 hours 45 minutes · 0.75 x 60 = 45 minutes, so 2 hours 45 minutes.
Worksheet · LightMySky