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### Question

A box contains 83 red balls and an unknown number of blue balls. If the probability of drawing a blue ball is 5 times the probability of drawing a red ball, then how many blue balls are there in the box?

**A**

415.

**B**

420.

**C**

410.

**D**

425.

**Soln.**

**Ans: a**

Let the number of blue balls be x. Chances of drawing a blue ball are $x/{x + 83}$ = 5 × $83/{x + 83}$, which gives x = 5 × 83 = 415.