Raffles Girls Pri Sch 2007 PSLE Math Prelim Q44

A group of pupils sat for two tests, test A and test B. The number of pupils who failed test A was 1/7 of those who passed test A. Given that there were 20 pupils who failed test A,

(a) How may pupils passed test A?
(b) The number of pupils who failed test B was 1/4 of those who failed test A. What fraction of the pupils passed test B?

Solution



(a)
1 unit ----- 20
7 units ----- 20 x 7 = 140

Answer: 140 pupils

(b)
Failed Test A ----- 20
Failed Test B ----- 1/4 x 20 = 5

(Total number of pupils)
8 units ----- 8 x 20 = 160

Fraction of pupils who failed Test B
5/160 = 1/32

Fraction of pupils who passed Test B
1 – 1/32 = 31/32

Answer: 31/32