CAT 2007 Stuffs

Q1. A = 333....333(51 digits), B = 666...666(51 digits) Find 52nd digit of (AXB) from the right.

(a)7,

(b)9,

(c)1,

(d)2.

 

Q2. 10000! = (100!)^k - P . P is prime number & P,k both are integers.

(a)105,

(b)106,

(c)104,

(d)102,

(e)None of these.

 

Those who can solve the qs plz give explanation of these two stuffs.

 

Regards,

Dipanjan.

__________________

n/a

Sorry 4 the mistake in QS

Sorry 4 the mistake in QS NO. 2. Tht qs is:

Q2. 10000! = (100!)^k - P . P is prime number & P,k both are integers.Find the max value of k.

(a)105,

(b)106,

(c)104,

(d)102,

(e)None of these.

Thank You in Advance,

Dipanjan

__________________

n/a

1st ans=7

trail n error method

considrr...33*66

3rd digit 4m right =7

sim..333*666

4th digi 4m right=7

 

Soln to q1

By mere observation we see that
3x6=18 ... 1 digit number and second digit from right in ans is 1
33x66=2178 ... 2 digit number and third digit from right in ans is 1
333x666=221778 ... 3 digit number and fourth digit from right in ans is 1
....
Thus since in q, its a 51 digit no, 52nd digit from right is 1

Also we can note that, from 52nd digit onwards till the leftmost digit all digits are 2, 51st digit is 1, 2nd to 50th digits are all 7 and units place is 8..

.

oops..i took it 4m left

Soln. 1

when we observe the pattern, for 33X66=2178   ( 3rd digit from right is 1)

                                                      333X666= 221778  ( 4th from right is 1)

                                             3333X6666 = 22217778 ( 5th digit from right is 1)........

So the answer will be    c) 1

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