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### Question

A box contains 2 navy, 4 red and 6 sky blue marbles. What is the probability of drawing a marble that is not sky blue if 2 marbles are drawn out randomly?

**A**

${5/22}$.

**B**

$6/12$.

**C**

$6/66$.

**D**

$10/66$.

**Soln.**

**Ans: a**

Total number of marbles is 12. Combinations of 2 marbles that are possible = ^{12}C_{2} = ${12 × 11}/2$ = 66. Chances of drawing a non-sky blue ball are ^{6}C_{2} = $(6 × (6 - 1))/2$ = 15. So probability = 15/66 = ${5/22}$.