Question

Example 2: The ratio of the number of boys to the number of girls in a school of 720 students is
3:5. If 18 new girls are admitted in the school, find how many new boys may be admitted so
that the ratio of the number of boys to the number of girls may change to 2:3.​

Answer 1

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Answer 2

Ratio of no. girls to no. of boys = 3:5

➢ Let no. of girls = 3x

➢ Let no. of boys = 5x

➢ Let this ratio be = 3x:5x

Total no. of students = 270

↣ 3x + 5x = 270

↣ 8x = 270

↣ x = 270/9

↣ x = 90

∴ No. of girls = 3×90 = 270

∴ No. of boys = 5×90 = 450

➢ Now, 18 boys are added.

No. of boys = 468

Let the new ratio of no. girls to no. of boys=2x:3x

↣ 3x = 468

↣ x = 468/3

↣ x = 156

∴ New no. of girls = 156 × 2 = 312

∴ No. of girls to be added = 312-270 = 42

Your answer = 42