PS Practice test question #8

The answer should be E.

4 can come at units digits 6 times
3 can come at units place 6 times
similarly for 2 and 1.

4*6=24
3*6=18
2*6=12
1*6=6
total=60

units place =60
6 will carry over to tens place =66
similarly 6 will keep on carrying over till thousands place

Hence the answer 66660.

You can also identify the pattern in the options.

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sudhir3127: Legendary Member; Posts: 829; Joined: Mon Jul 07, 2008 10:09 pm; Location: INDIA; Thanked: 84 times; Followed by:3 members

Re: PS Practice test question #8

by sudhir3127 » Thu Aug 21, 2008 10:33 pm

missionmba wrote:the answer was D or E

i picked E thinking 6 carry will make tens digit 6.

u need to know the formula for
"if all the possible n digit numbers using n distinct digits are formed ..then the sum of all the numbers so formed asre equal to

(n-1)!* ( sum of all the digits)* (1111........n terms)

we have 4 distinct digits

hence

(4-1)!*( 1+2+3+4) *(1111) ( since we have only 4 numbers)

6*10*1111 = 66660

hope that helps..

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bluementor: Master | Next Rank: 500 Posts; Posts: 418; Joined: Wed Jun 11, 2008 5:29 am; Thanked: 65 times

by bluementor » Fri Aug 22, 2008 3:45 am

Another way to look at this problem is as follows:

You can divide the the entire set of 24 numbers into two groups, the first 12 numbers(Group A)and the last 12 numbers(Group B).

You will find that for every number in group A, you will be able to match it with a number Group B so that when they are added up, you will get the value of 5555.

For example:

1234 + 4321 = 5555
1243 + 4312 = 5555
... and so on.

So summing up all 24 numbers, you will get 12x5555 = 66660.

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