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

Question 94 Probability Exercise 13.1

12 defective pens are accidently mixed with 132 good ones. It is not possible to just look at pen and tell whether or not it is defective. One pen is taken out at random from this lot.

Determine the probability that the pen taken out is good one.



Events in probability are characterized as certain probable outcomes of an experiment that make up a subset of a finite sample space. Every event will always have a probability of occurrence between 0 and 1.

We have,

No. of good pens = 132

No. of defective pens = 12

So, the total no. of pens = 132 + 12 = 144

Then, the total no. of possible outcomes = 144

Now, let E = event of getting a good pen.

No. of favourable out comes = 132 {132 good pens}

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

P(E) = 132/144 = 11/12

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