# RD Sharma Solutions Class 10 Mathematics Solutions for Probability Exercise 13.1 in Chapter 13 - Probability

Question 71 Probability Exercise 13.1

A bag contains 5 red, 8 white and 7 black balls. A ball is drawn at random from the bag. Find the probability that the drawn ball is not black.

Solution:

When one event happens if and only if the other one doesn't, two occurrences are said to be complimentary. The probability of two complementary events add up to one.

Total number of possible outcomes = 20 (5 red, 8 white & 7 black}

Let E = event of getting a black ball

No. of favourable outcomes =7 (7 black balls)

Probability, P(E) = Number of favourable outcomes/ Total number of outcomes

P(E) = 7/20

\overline{\mathrm{E}}=\text { Event of not getting black ball }

\begin{aligned} &P(\overline{\mathrm{E}})=1-P(E) \\ &P(\overline{\mathrm{E}})=1-\frac{7}{20} \\ &P(\overline{\mathrm{E}})=\frac{13}{20} \end{aligned}

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