S-Cool Revision Summary

S-Cool Revision Summary

Fractions

Basic skills: Cancelling, improper to mixed numbers, multiplying, dividing, adding, subtracting.

Always change mixed numbers to improper fractions before doing calculations!

Finding fractions of quantities - multiply by the top, divide by the bottom.

Ratio - find the total number of parts before dividing.

Decimals

Basic skills: Adding, subtracting, multiplying, dividing.

Changing Between

Fractions and Decimals

Percentages

To write an amount as a percentage:

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Finding a percentage of a quantity:

  1. Change the % to a decimal (divide by 100).
  2. Multiply by the original quantity.

Increasing/decreasing a quantity by a percentage:

  1. Find new percentage after increase/decrease (100 - % increase/decrease).
  2. Change it to a decimal (divide by 100).
  3. Multiply by the original quantity.

Compound interest:

  1. Add interest on to 100%.
  2. Change to a decimal (divide by 100).
  3. Multiply the original amount by this decimal for each year.