Numbers

Decimals, Fractions and Percentages:

What are decimals? 

A type of number with a point e.g 3.3, 20.5, 300.43

Each unit after the decimal point has its own classification e.g. tenths, hundredths, thousandths and so on.

Multiplying Decimals:

1. First, remove the decimal point as if you are multiplying whole numbers.
2. Count the number of digits that are after the decimal point in both numbers. 
3. Place the decimal point before the number of digits calculated in step 2.

Example:

Q) 0.5 x 0.8

1. 5 x 8 = 40
2. There is one digit after the decimal point in both numbers – 1+1=2
3. Place decimal point before two digits – 0.40

A) 0.4

Tips:

When multiplying a number by 10 or any multiple of 10, you simply move the decimal point to the right

. e.g 0.75 x 10 = 7.5 → 10 has one 0 so we move the decimal point 1 space to the right

Dividing Decimals:

1. Multiply the denominator by 10 or any multiple of 10 to remove the decimal point
2. Multiply the numerator by the same number > this is so the ratio between the numerator and denominator stays the same
3. Do the division using the short division method

Example:

Q) 7.75 ÷ 0.62

1. Multiply 0.62 by 100 to remove the decimal point and turn it into a whole number
2. Multiply 7.75 (numerator) by 100 because we multiplied 0.62 (denominator) by 100
3. 775 ÷ 62

A) 12.5

Tips:

. When dividing by 10 or a multiple of 10, you move the decimal point to the left

. e.g. 95.7 ÷ 100 = 0.957 → 100 has two 0’s, so we move the decimal point 2 spaces to the left