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Mathematics · Probability · NCERT Examples

Example 7

A complete, independently verified solution for NCERT Example 7.

Mathematics · Chapter 14 · NCERT Examples

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NCERT Example

Example 7

student selection · girl · boy

A class has 40 students: 25 girls and 15 boys. One student's name card is drawn at random. Find the probability that the selected name is (i) a girl's and (ii) a boy's.

Solution

Board-exam working:

Total equally likely name cards=40\text{Total equally likely name cards}=40

(i) There are 25 favourable cards bearing girls' names.

P(girl)=2540=58P(\text{girl})=\frac{25}{40}=\frac58

(ii) There are 15 favourable cards bearing boys' names.

P(boy)=1540=38P(\text{boy})=\frac{15}{40}=\frac38

The probabilities add to 1, as expected.

58+38=1\frac58+\frac38=1

Final answer

(i) 58(ii) 38\boxed{\text{(i) }\frac58\qquad\text{(ii) }\frac38}