NDA 2019 Maths · Mathematics · Statistics · easy

The average marks of 30 students of one section are 60 and of 20 students of another section are 70. The average marks of all 50 students are

Single correct option

The average marks of

30

students of one section are

60

and of

20

students of another section are

70

. The average marks of all

50

students are

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Answer: (A) $64$

The combined mean is the weighted mean

\frac{30\cdot60+20\cdot70}{50}=\frac{1800+1400}{50}=64

. The simple mean

65

ignores the unequal group sizes; the combined mean must be closer to the larger section's average of

60

Original question written in the NDA 2019 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake