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EEJ MAIN Mathematics QUESTION #6980
Question 1

A box holds 15 green and 10 yellow balls. If 10 balls are picked one at a time with replacement, find the variance of the number of green balls picked.

  • $\dfrac{12}{5}$✔️
  • 6
  • 4
  • $\dfrac{6}{25}$
Correct Answer Explanation

This is a binomial experiment: $n=10$, $p=P(\text{green})=\dfrac{15}{25}=\dfrac{3}{5}$, $q=\dfrac{2}{5}$.

$\text{Variance} = npq = 10 \times \dfrac{3}{5} \times \dfrac{2}{5} = 10 \times \dfrac{6}{25} = \dfrac{60}{25} = \dfrac{12}{5}$