Question

How many 4 digits number contain the number 2.

a) 3170
b)3172
c)3174
d)3168; How many 4 digits number contain the number 2.; a) 3170; b)3172; c)3174; d)3168

Answer 1

this question answer is d)

Answer 2

hey.......
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Number of 4 - digit numbers with 2 = ( Number of 4 - digit number ) - ( Number of 4 - digit numbers without 2 ) .

So again we will be redirected into permutations.

We have conditions that repetition is allowed. We have 10 numbers to be filled in 4 place. Since 0 can't be in thousands place , the number of 4 - digit numbers will be 9*10*10*10 = 9000 .

To find number of number without 2 we have repetition allowed with 9 numbers in 4 place. Since 0 can'tbe in first place. Number of 4 - digit numbers without 2 will be 9*9*9*8 = 5832.

So as said earlier the answer will be 9000 - 5832 = 3168..
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.hence Options D is correct answer
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i hope this helps u.
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