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Exponent of 12 in 50! is
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12 = 22 × 3
Exponent of 12 in 50! = min{E2(50!), E3(50!)}
= E3 (50!) = 22
The number of zero's at the end 60! of is
Number of zero's at the end of 60! = exponent 10 in
60! = min{E2 (60!), E5 (60!)}
= E5 (60!) = 14.
Three dice are rolled. The number of possible outcomes in which at least one die shows 6 is :
Total number of outcomes = 6 × 6 × 6 = 216
Number of outcomes in which none of the dice shows 6 = 5 × 5 × 5 = 125
∴ Number of outcomes in which at least one die shows 6 = 216 - 125 = 91
The maximum number of points of intersection of 8 circles, is
Two circles intersect in 2 points.
∴ Maximum number of points of intersection
= 2 × number of selection of two circles from 8 circles
= 2 × 8C2 = 2 × 28
= 56.
Let 1 ≤ m < n ≤ p. The number of subsets of the set A = {1, 2, 3,…p} having m,n as the least and the greatest elements respectively, is
Total number of subject = the number of selections of at least two elements including m, n and natural numbers lying between m and n= total number of selections from n-m-1 different things 2n - m - 1
The number of odd proper divisors of 3p . 6m. 21n is
3p. 6m. 21n = 2m . 3p + m + n . 7n
∴ The required number of proper divisors
= Number of selection of any number of 3's and 7's
[∴ For odd divisors 2 must not be selected]
= (p + m + n + 1)(n + 1) - 1.
The number of even proper divisors of 1008 is
1008 = 24 × 32 × 7
∴ The required number of even proper divisors
= total number of selections of at least one 2 and any number of 3's or 7's
= 4 × (2 + 1) × (1 + 1) - 1 = 23.
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