15 boys and a certain number of girls appeared for a test. The average score of the boys was 26, the average score of the girls was 36, and the combined average score was 30. How many girls appeared for the test?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1 i.e. 10.
We know that,
Average = Sum of observations/Number of observations
Let the number of girls be x
According to the question:
⇒ 15 × 26 + x × 36 = (15 + x) × 30
⇒ 390 + 36x = 450 + 30x
⇒ 6x = 60
⇒ x = 10
Hence, the number of girls who appeared for the test was 10