Synopsis IAS

Answer

Solution

UPSC Prelims

Mathematics

Theme:

Permutation and Combination / क्रमचय और संचय

Q73 2016, Permutation and Combination

How many numbers are there between 100 and 300 which either begin with or end with.2?

102, 112, ..... 192 (Total 10)

202, 212, ..... 292 (Total 10)

200, 201, 202, ..... 299 (Total 100) of which 10 end with 2 so subtract that.

Hence, answer is (a). Remember either begin with or end with 2 means we cannot double count those that both begin with and end with 2.

Q 73. 2016, Permutation and Combination