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Mathematics · Probability · NCERT Examples

Example 3

A complete, independently verified solution for NCERT Example 3.

Mathematics · Chapter 14 · NCERT Examples

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NCERT Example

Example 3

die · complementary events

A fair die is thrown once. Find the probability of getting (i) a number greater than 4 and (ii) a number less than or equal to 4.

Solution

Board-exam working:

S={1,2,3,4,5,6},n(S)=6S=\{1,2,3,4,5,6\},\qquad n(S)=6

(i) Numbers greater than 4 are 5 and 6.

E={5,6},n(E)=2E=\{5,6\},\qquad n(E)=2
P(E)=26=13P(E)=\frac26=\frac13

(ii) Numbers less than or equal to 4 are 1, 2, 3 and 4.

F={1,2,3,4},n(F)=4F=\{1,2,3,4\},\qquad n(F)=4
P(F)=46=23P(F)=\frac46=\frac23

Final answer

(i) 13(ii) 23\boxed{\text{(i) }\frac13\qquad\text{(ii) }\frac23}