Q1. The ratio of the number of boys and girls in a school is 5 : 6. If the annual percentage increase in the number of boys and girls is 20% and 30% respectively, what will be the new ratio after one year?
A 11 : 17
B 10 : 11
C 10 : 13 Correct
D 11 : 13
Explanation
Take the original numbers as 5x boys and 6x girls. After a 20% annual increase, boys become 5x × 120/100 = 6x. After a 30% annual increase, girls become 6x × 130/100 = 7.8x. The new ratio is 6 : 7.8, which becomes 60 : 78 and then 10 : 13. The ratios 11 : 17, 10 : 11 and 11 : 13 do not follow from applying the two different percentage increases to the two original quantities.