A school had 120 students with an average age of 20 years. Later, a new batch of students joined. After their inclusion, the average age dropped to 19.5 years, even though the newcomers had an average age of 18 years. Find the number of students in the new batch.
A.35
B.30
C.40✓ Correct
D.45
Explanation
Let new batch size = n. Total age before = 120×20 = 2400. After: (120+n)×19.5 = 2400 + 18n. Solving: 2340 + 19.5n = 2400 + 18n → 1.5n = 60 → n = 40.
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