NCERT Solutions Class 10 Mathematics Solutions for Probability - Exercise 15.1 in Chapter 15 - Probability

Question 17 Probability - Exercise 15.1

A lot consists of 144 ball pens of which 20 are defective and the others are good. Nuri will buy a pen if it is good, but will not buy if it is defective. The shopkeeper draws one pen at random and gives it to her. What is the probability that she will buy it?


The total numbers of outcomes i.e. pens = 144

Given, numbers of defective pens = 20

∴ The numbers of non defective pens = 144-20 = 124

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

Total numbers events in which she will buy them = 124

So, P (buying) = 124/144 = 31/36 = 0.86

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