Quantitative Reasoning- Ratio and Proportion – what is R.O.P?

QNR 1. In a class there are 6 more girls than boys, and the ratio of boys to girls is 2 to 5. How many students are there in this class?

(i) 21

(ii) 11

(iii) 13

(iv) 14

Ans: We know how to solve this using equations; let us approach it using different methods. (R.O.P -> Rejecting Out Options).

a) The fastest method, in our opinion is -> if boys are ‘b’ in number, girls are ‘b+6’. Total students = 2b + 6. “2b +6” is an EVEN number. Option (iv) 14.

b) Second method: Since, boys to girls ratio is 2:5, we can assume boys, girls to be 2a, 5a. Total students = 7a. We can reject out option (ii) and (iii). Also 5a – 2a = 3a = 6 (given) => a = 2. Total students = 7×2= 14. Option (iv) 14.

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