Question

How many num are their between 99 and 1000 having atleast one of digit 7?

Answer 1

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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 (Ans)

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