Maths Topic 12 - Decimals


Decimals – Subtraction, Addition, Multiplication, Division, Decimals to Fractions. These maths skills are commonly tested in 11+ exams and Selective School exams in the UK.

Examples

Example Question 1:

(a) 3.6 × 1.4 = ?

(b) 29.9 ÷ 2.3 = ?

Answers: (a) 5.04  (b) 13

Explanations: 

(a) First take out the decimal points and multiply 36 × 14 = 504. Next, counting from the right to the left, put back the decimal point for the same number of places as the number of decimal digits in the sum (the decimal numbers were .6 and .4) = 2 decimal places → 5.04

(b) First multiply both the divisor (2.3) and the dividend (29.9) by 10 so that the decimal point is gone from the divisor. You are left with the sum 299 ÷ 23 = 13

Example Question 2:

(a) What is 0.8 as a fraction?

(b) What is 0.14 as a fraction?

(c) What is 1/7 as a decimal?

Answers: (a) 4/ (b) 7/50  (c) 0.14

Explanations:

(a) The first decimal place is tenths, so 0.8 = 8/10 which is simplified to 4/ 

(b) The first decimal place is tenths and the second decimal place is hundredths, so 0.14 = 14/100  which is simplified to 7/50

(c) Divide the numerator (1) by the denominator (7) to 3 decimal places and then round it to two places: 1 ÷ 7 = 0.142 which is rounded to 0.14

Video Tutorials

Subtraction – Column

 

Addition – Column

 

Multiplication

 

Division

 

Division

 

Decimals to Fractions – Part 1

 

Decimals to Fractions – Part 2