A box contains only black and white pencils

MATHEMATICS · Subjective · CBSE · Mathematics · Algebra Play · Algebra Play

Problem

A box contains only black and white pencils. The probability of drawing a black pencil from the box is 0.60.6. After 12 white pencils are added to the box, the probability of drawing a black pencil becomes 0.50.5. Find the original number of black pencils in the box.

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