# 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

## Percentages

**To write an amount as a percentage:**

**Finding a percentage of a quantity:**

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

**Increasing/decreasing a quantity by a percentage:**

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

**Compound interest:**

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