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Re: If a, b, c, and d are positive integers, what is the value of (a + b) [#permalink]
Nidzo wrote:
1)

Given that factorials are the product of the number itself and of all positive integers preceding it, the only way that \(4*a!\) equals the factorial \(b!\) is if \(b = 3\) and \(a = 4\).

Therefore we have \((3+4)(c+d)\). However, we have no information on C and D though.

INSUFFICIENT


2)

Here \(d = 5\), and \(c = 4\) for the same reason as mentioned in 1).

Here we have \((a+b)(4+5)\). No information regarding a and b.

INSUFFICIENT



1+2) Together we get: \((3+4)(4+5)\)

\(7*9= 63\)

SUFFICIENT


ANSWER C



Here a=3 and b=4, not vice versa.
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Re: If a, b, c, and d are positive integers, what is the value of (a + b) [#permalink]
If a, b, c, and d are positive integers, what is the value of (a + b)(c + d)?

(1) 4*a! = b!
(2) 5*c! = d!

Hi Experts,

Can someone pls explain how is it C?
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Re: If a, b, c, and d are positive integers, what is the value of (a + b) [#permalink]
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