Mathematics · 2023
JEE Main · 31 January 2023, Shift 2 · Q79
Let the mean and standard deviation of marks of class A of 100 students be respectively 40 and α (> 0 ), and the mean and standard deviation of marks…
Let the mean and standard deviation of marks of class A of $\displaystyle 100$ students be respectively $\displaystyle 40$ and $\displaystyle \alpha$ (> $\displaystyle 0$ ), and the mean and standard deviation of marks of class B of n students be respectively $\displaystyle 55$ and $\displaystyle 30$ $\displaystyle -\alpha$. If the mean and variance of the marks of the combined class of $\displaystyle 100+\mathrm{n}$ studants are respectively $\displaystyle 50$ and $\displaystyle 350$ , then the sum of variances of classes A and B is :
Official answer
From NTA’s final answer key for this paper.
(3)
$\displaystyle 900$
(4)
$\displaystyle 500$
NTA’s answer key accepts either.
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JEE Main 2023 Mathematics question, with the answer from NTA’s final answer key. Where our answers come from.