O Level E Maths Tuition Singapore/Tuition O Level E Maths/Tutor
Addition and Subtraction of Fractions
1. Add/subtract the whole numbers first.
2. Find the lowest common multiple (LCM) of the fractions and convert them into fractions with the same denominators before adding/subtracting the fractions.
Example 1
3/5 + 1/4
= 12/20 + 5/20 (LCM is 20)
= 17/20
Example 2
-3 1/2 – (-2 2/3)
= -3 1/2 + 2 2/3
= -1 -1/2 + 2/3 (LCM 6)
= -1 -3/6 + 4/6
= -1 + 1/6
= -5/6
Multiplication of Fractions
1. Convert all mixed numbers to improper fractions first.
2. Simplify the fractions first by ‘cancelling’, to see if anything will divide into any of the top numbers and also the bottom numbers.
3. Multiply the numerators, then the denominators together
Evaluate
a) 8/9 x 3/4
b) -1 2/5 x 2/3
c) 2 1/2 x 3 1/5
Ans
(a) 2/3 (b) – 14/15 (c) 8
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