The ratio of the number of boys and girls in a school was 5: 3. Some new boys and girls were admitted to the school, in the ratio 5: 7

The ratio of the number of boys and girls in a school was 5: 3. Some new boys and girls were admitted to the school, in the ratio 5: 7. At this time, the total number of students in the school became 1900, and the ratio of boys to the girls changed to 7: 5. the number of students in the school before new admissions was!

(a) 133

(b) 152

(c) 171

(d) 190

Sol:

By cross multiplication method

4 unit → 24 x

1 unit → 6x

Now, 8unit + 12x → 1900

⇒ 8unit + 2unit → 1900

⇒ 8 unit → 19 × 8

= 152