Red Swastika Sch 2011 PSLE Math Prelim Paper 2 Q8

The ratio of the number of apples in Box A to the number of apples in Box B is 3 : 2. All the apples in Box B are green. The ratio of the number of green to the number of red apples in Box A is 4 : 5. There are 20 more green apples in Box B than in Box A. How many red apples are there?

Solution

* 4 units of green apples + 5 units of red ---- 9 units in Box A
** 3 units in Box A (x 3) ---- 9 units, hence 2 units in Box B (x 3) will give 6 units.  

Green Apples
Box B - Box A ----- 20
6 units - 4 units ----- 20
2 units ----- 20
1 unit ----- 20 divided by 2 = 10

Red Apples
5 units ----- 5 x 10 = 50

Answer: 50 red apples

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