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Flashcards · Maths · Number Without a Calculator

Place Value, Negatives and the Four Operations

17 cards

  1. What is the value of the digit 6 in 4.263?

    6 hundredths, which is 0.06.

  2. How do you order decimals such as 0.45, 0.405 and 0.54?

    Write them to the same number of decimal places (0.450, 0.405, 0.540) and compare digit by digit from the left.

  3. What happens to the digits when you multiply by 100?

    Each digit moves two columns to the left and the decimal point stays put, so \(3.2 \times 100 = 320\).

  4. How do you work out \(2.4 \times 0.35\) without a calculator?

    Multiply \(24 \times 35 = 840\), then give the answer three decimal places in total: 0.84.

  5. How do you work out \(8.4 \div 0.07\)?

    Multiply both numbers by 100 so the divisor is whole: \(840 \div 7 = 120\).

  6. How does the grid method work for \(34 \times 27\)?

    Split into \(30 + 4\) and \(20 + 7\), multiply each pair to get 600, 80, 210 and 28, then add them: 918.

  7. What is \(3 - (-5)\)?

    8, because subtracting a negative is the same as adding.

  8. What is \((-4) \times (-6)\)?

    24. The signs are the same, so the answer is positive.

  9. What is \((-20) \div 5\)?

    \(-4\). Different signs give a negative answer.

  10. What does BIDMAS stand for?

    Brackets, Indices, Division and Multiplication, Addition and Subtraction.

  11. What is \(24 \div 4 \times 3\)?

    18. Division and multiplication have equal priority, so work from left to right.

  12. What is \((-4)^2\), and how is it different from \(-4^2\)?

    \((-4)^2 = 16\) because the bracket squares the negative too, whereas \(-4^2 = -16\).

  13. How do you estimate \(38 \times 21\)?

    Round each number to 1 significant figure: \(40 \times 20 = 800\).

  14. 250 people travel on coaches with 48 seats. How many coaches are needed?

    6. \(250 \div 48 = 5\) remainder 10, and the last 10 people still need a coach.

  15. What is the difference between \(-12\) and 3?

    15, because \(3 - (-12) = 15\).

  16. Why is \(0.2 \times 0.4\) not 0.8?

    \(2 \times 4 = 8\), but there are two decimal places in total, so the answer is 0.08.

  17. How do you check a division such as \(4872 \div 12 = 406\)?

    Multiply the answer by the divisor: \(406 \times 12 = 4872\).