Standard Mathematics Primary 6 Ratio

In a class, the ratio of the number of boys to the number of girls is 3 : 5. After 6 more boys joined the class (no girls left or joined), the new ratio of boys to girls became 1 : 1. Find the ORIGINAL number of students in the class.

A 30
B 24
C 18
D 9
Show Worked Solution

Worked Solution

Step 1: Let the original number of boys = 3u and girls = 5u (one unit u to be found). Step 2: After 6 boys join, the new boys count is 3u + 6, and the girls count is unchanged at 5u. The new ratio is 1 : 1, so 3u + 6 = 5u. Step 3: Solve for u. 2u = 6, so u = 3. Step 4: Find the original numbers. Boys = 3 × 3 = 9. Girls = 5 × 3 = 15. Step 5: Original total = 9 + 15 = 24. Answer: 24

Correct answer: 24

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