Latest self Aptitude Question SOLUTION: 21!=510909x21y1709440000 Without calculating 21!, what are the digits marked x and y? explain.

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(#M40010031) SELF question Keep an EYE

21!=510909x21y1709440000

Without calculating 21!, what are the digits marked x and y? explain.

jyotish r (11 years ago)

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chaitanya  (11 years ago)

Sum of the digits should be divisble by 9

Sum of the digits is 52 so r is 2 so (x+y)mod9=2
Possibilities is (1,1) (2,0)

Also sum of the digits will be divisble 11
Since sum of the digits is 52 and x and y are at even and odd places

so (x-y)mod11--- R is minimum=3
So that rules out (x+y)mod9=2 and then it should be 11

Various possibilities of 11 (7,4),(9,2),(8,3)....
But 7-4=3

So digits are 7,4

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Aman  (11 years ago)

x=4 and y=7

because it should be divisible by 9 and 11.
check for divisibility of 9 and 11 and solve the two equations.

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Sneha paliwal  (11 years ago)

ans x=4 and y=7.because by put that value no.is completely divisible by 21.

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