Question

# A box contains some black balls and 30 white balls. If the probability of drawing a black ball is two-fifths of a white ball, find the number of black balls in the box. [3 MARKS]

Solution

## Steps: 2 Marks Answer: 1 Mark Let the number of black balls be x Then total balls =x+30 P (black balls) =xx+30 P(white balls) =30x+30 But xx+30=25×30x+30 ⇒5x=60⇒x=12 ∴ Number of black balls =12.

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