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Flashcards · Maths · Number Without a Calculator

Fractions, Decimals and Percentages

18 cards

  1. What does per cent mean?

    Out of every hundred.

  2. Write 35% as a fraction in its simplest form.

    \(\dfrac{35}{100} = \dfrac{7}{20}\).

  3. How do you change a fraction to a percentage?

    Divide the top by the bottom to get a decimal, then multiply by 100: \(\dfrac{3}{8} = 0.375 = 37.5\%\).

  4. What are \(\dfrac{1}{8}\) as a decimal and as a percentage?

    0.125 and 12.5%.

  5. What are \(\dfrac{1}{3}\) and \(\dfrac{2}{3}\) as percentages?

    \(33\dfrac{1}{3}\%\) and \(66\dfrac{2}{3}\%\).

  6. How do you find 35% of \(\pounds 240\) without a calculator?

    10% is 24, 30% is 72 and 5% is 12, so 35% is \(\pounds 84\).

  7. How do you find 17.5% of \(\pounds 640\)?

    10% is 64, 5% is 32 and 2.5% is 16, so the total is \(\pounds 112\).

  8. What is the multiplier for a 12% increase?

    1.12.

  9. What is the multiplier for an 8% decrease?

    0.92.

  10. What is the formula for percentage change?

    Change \(\div\) original \(\times\) 100.

  11. A price rises from \(\pounds 40\) to \(\pounds 47\). What is the percentage increase?

    \(\dfrac{7}{40} \times 100 = 17.5\%\).

  12. A price is \(\pounds 84\) after a 20% increase. How do you find the original price?

    \(\pounds 84\) is 120%, so divide by 1.2: \(\pounds 70\).

  13. A coat costs \(\pounds 63\) after a 25% reduction. What was the original price?

    \(\pounds 63\) is 75%, so 25% is \(\pounds 21\) and 100% is \(\pounds 84\).

  14. Why can you not just add 25% of the sale price back on to find the original?

    The 25% was taken off the original price, not off the sale price.

  15. Which fractions give terminating decimals?

    Those whose denominator, in simplest form, has only 2 and 5 as prime factors, such as \(\dfrac{7}{20}\).

  16. What is simple interest?

    Interest worked out on the original amount only, so it is the same every year.

  17. What is the total for \(\pounds 800\) at 4% simple interest for 3 years?

    4% is \(\pounds 32\) a year, so interest is \(\pounds 96\) and the total is \(\pounds 896\).

  18. What does \(0.\dot{3}\) mean?

    0.333... recurring, which is \(\dfrac{1}{3}\).