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Re: If a, b, c, and d are positive integers, what is the value.. [#permalink]
22 Dec 2012, 07:22

1

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If a, b, c, and d are positive integers, what is the value of (a + b)(c + d)? (1) 4a! = b! (2) 5c! = d!

Hi,

Statement 1: 4a! = b! so (a,b) have only one valid case (3,4) so values are a=3 and b=4 Statement 1: 5c! = d! so (c,d) have only one valid case (4,5) so values are c=4 and b=5

Re: If a, b, c, and d are positive integers, what is the value.. [#permalink]
22 Dec 2012, 07:25

3

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700+ questions are never much difficult,they are just tricky...

In this problem if you can see carefully, only one combination of a and b satisfies 4a! = b!...well, how's that? simple for a=3... a! will be 3*2*1 and 4*a! will be 4*3*2*1 i.e. 4! so b=4...no other value of a would satisfy this.. Same is the case with 5c! = d! .i.e c=4 and d=5.

Sentence 1: not sufficient as it gives only the values of a & b Sentence 2: not sufficient as it gives only the values of c & d

both sentences together: can solve the problem as we get all the values

Re: If a, b, c, and d are positive integers, what is the value.. [#permalink]
22 Dec 2012, 08:18

daviesj wrote:

700+ questions are never much difficult,they are just tricky...

In this problem if you can see carefully, only one combination of a and b satisfies 4a! = b!...well, how's that? simple for a=3... a! will be 3*2*1 and 4*a! will be 4*3*2*1 i.e. 4! so b=4...no other value of a would satisfy this.. Same is the case with 5c! = d! .i.e c=4 and d=5.

Sentence 1: not sufficient as it gives only the values of a & b Sentence 2: not sufficient as it gives only the values of c & d

both sentences together: can solve the problem as we get all the values

Re: If a, b, c, and d are positive integers, what is the value.. [#permalink]
23 Dec 2012, 03:28

If a, b, c, and d are positive integers, what is the value of (a + b)(c + d)? (1) 4a! = b! (2) 5c! = d! all u need to know are values of positive integers a,b,c &d. statement1:talks about only a and b .no info reg c&d .insuff statement2:talks about only c&d.no info reg a&b.insuffi. combining 1 &2 only values which will work for a&b are a=3,b=4,c&d are c=4,d=5.sufficient. C is the answer

Re: If a, b, c, and d are positive integers, what is the value.. [#permalink]
02 Mar 2013, 11:24

daviesj wrote:

700+ questions are never much difficult,they are just tricky...

In this problem if you can see carefully, only one combination of a and b satisfies 4a! = b!...well, how's that? simple for a=3... a! will be 3*2*1 and 4*a! will be 4*3*2*1 i.e. 4! so b=4...no other value of a would satisfy this.. Same is the case with 5c! = d! .i.e c=4 and d=5.

Sentence 1: not sufficient as it gives only the values of a & b Sentence 2: not sufficient as it gives only the values of c & d

both sentences together: can solve the problem as we get all the values

hence the answer 'C'

Hope the point is clear..:)

Hi Daviesj Thanks a lot.your explanation has answered all my questions