Advanced Mathematics Primary 4 Fractions

A bag of marbles contains red, blue and green marbles. 3/8 are red. 1/3 of the remainder are blue. The rest (50 marbles) are green. Find the total number of marbles in the bag.

A 120
B 100
C 150
D 75
Show Worked Solution

Worked Solution

Step 1: Red = 3/8 of total. Remainder after red = 5/8 of total. Step 2: Blue = 1/3 of remainder = 1/3 × 5/8 = 5/24 of total. Step 3: Green = remaining = 5/8 − 5/24 = 15/24 − 5/24 = 10/24 = 5/12 of total. Step 4: Green = 50 marbles, so 5/12 × Total = 50, hence Total = 50 × 12/5 = 120. Answer: 120

Correct answer: 120

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