A bhag contain 15 white balls and some black balls. If probability of drawing a black ball from the bag is thrice that of drawing a white ball, find the number of black balls in the bag.

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Solution

No. of white balls $= 15$
let the no. of black balls $= x$
probability of drawing a white ball $= \frac{15}{(15 + x)}$
probability of drawing a black ball $= \frac{x}{(15 + x)}$
Given condition-
$\frac{x}{(15 + x)} = 3 \times \frac{15}{(15 + x)}$
or, $x = 3 \times 15$
or, $x = 45$
Number of black balls $= 45$ .

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A bhag contain 15 white balls and some black balls. If probability of drawing a black ball from the bag is thrice that of drawing a white ball, find the number of black balls in the bag.

No. of white balls=15let the no. of black balls =xprobability of drawing a white ball =15(15+x)probability of drawing a black ball =x(15+x)Given condition-x(15+x)=3×15(15+x)or, x=3×15 or, x=45Number of black balls =45.