Question

How many numbers are there between 99 and 1000 having at least one of their digits 7

Answer 1

Heya




Your answer is :

Total number of 3 digit numbers having atleast one of their digits as 7 ,
= (Total numbers of three digit numbers) – (Total number of 3 digit numbers in which 7 does not appear at all).
= (9 × 10 × 10) – (8 × 9 × 9)
= 900 – 648 = 252.


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