Hokkien Huay Kuan Combined Primary 2010 PSLE Math Prelim Paper 2 Q9

The number of pens in Box X and Box Y are in the ration of 3:2. All the pens in Box Y are green. The ratio of green pens to blue pens in Box X is 4:5. There are 12 more green pens in Box Y than in Box X. How many blue pens are there?

Solution

Green in Box X
(4/9) x (3/5) = 4/15

There are 12 more blue pens in Box X than in Box Y
(2/5) - (4/15) ----- 12
(6/15) - (4/15) ----- 12
2/15 ----- 12
1/15 ----- 12 divided by 2 = 6

Blue Pens
(5/9) x (3/5)
= 1/3
= 5/15

5/15 ----- 5 x 6 = 30

Answer: 30 blue pens

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