Zoe X. answered • 06/09/15

Tutor

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Zoe - Pre-calculus, Calculus, Algebra I & II

You have a total of 7+8 = 15 balls. Since 7 of them are red, you have a 7/15 chance of drawing a red ball. Likewise, since 8 are green, you have an 8/15 chance of drawing a green ball. Since we replace the ball after each draw, the chance of drawing a red ball again is still 7/15. The draws are independent of one another.

Since you're drawing 4 times, the probability of drawing 4 in a row is:

(7/15) * (7/15) * (7/15) * (7/15) = (7/15)

^{4}The result is your answer.