30 students collected money for a donation, and the average contribution was Rs 50. Later, their teacher also contributed some money, and the average contribution became Rs 57. How much did the teacher contribute?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Rs 267
The total collected is the average multiplied by the number of contributors. The teacher’s share is the new total minus the students’ total.
Total from 30 students \(=30\times50=1500\)
Total from 31 contributors \(=31\times57=1767\)
Teacher’s contribution \(=1767-1500=267\)
The teacher contributed Rs 267.