Operations On Fractions JSS1 Mathematics Lesson Note

Operation on Fractions

Addition and Subtraction 

Example 1: Find the value of the following: (a) 4/9 + 5/9 + 7/9  (b) ⅝ – ⅜   (c) 1 + 4/7

Solution:

(a): 4/9 + 5/9 + 3/9  = 16/9   (since the denominators are the same, we just add the numerators together.)

(b): ⅝ – ⅜   = 2/8   (since the denominator is the same, we just subtract the numerators from each other)

Try these questions yourself

Example 2: Simplify the following (a)  33/4 + ⅝ + 17/12    (b) 2 + 42/5  – 5 3/5

Solution:

(a)   33/4 + ⅝ + 17/12 

(198 + 15 + 34)/24 = (find the LCM of the fraction, then add the whole together; the LCM is 24)

= (247/24) =    (convert the improper fraction to mixed numbers)

(b)  2 + 42/5  – 5 3/5

Solution:

 (rearrange by separating the whole numbers from fractions)

  =   5 + 2 – 3 = 4/5

   5  (same denominator)

Multiplication and division of fractions

Example 1: Simplify the following: (a) 4/5 * 2/3 (b) what is the product of 35/17, 2 5/6, and 4/8

(d) 3/5 ÷ 4/9 (d) 24/5 * 56/8 ÷ 51/9

Solution:

(a) 4/5 * 2/3 = 8/15( multiple the numerator and denominator together)

(b) (b) what is the product of 35/17, 2 5/6 and 4/8 = 56/17 * 17/6 *4/8

= 17 divides 17, 6 divides 56 also 4 divides 8

= 14/3 = 42/3

(c) 24/5 * 56/8 ÷ 51/9= 14/5 * 46/8 * 9/46(change to improper and also change the division sign to multiplication and also change the fraction up and down)

= 14/5 * 46/8 * 9/46 (46 divides 46 etc)

= 63/20 = 33/20