Practice Test Discussion

In an examination, a batch of 60 students made an average score of 55 and another batch of 40 made it only 45. What is the overall average score?

None of these

Explanation

According to the question

$n_{1} = 60, n_{2} = 40, a_{1} = 55, a_{2} = 45$

We know the formula,

Weighted average(Aw) $= \frac{n_{1} a_{1} + n_{2} a_{2}}{n_{1} + n_{2}}$

Average of combined group = $\frac{60 \times 55 + 40 \times 45}{60 + 40} = 51$

Hence, Option D is correct.

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