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anjaligeorge1: Senior | Next Rank: 100 Posts; Posts: 66; Joined: Wed Feb 20, 2008 6:23 pm; Thanked: 2 times

please help

by anjaligeorge1 » Thu Jun 19, 2008 6:04 am

If a*b*c=60, where a, b, and c are integers greater than 1, a+b+c=?

(1) a+b=8
(2) Both a and b are odd numbers.

the answer says B .why cant it be D coz a ,b , & c can be 3 , 5 , & 4
as per statement 1 - a+ b : 3 + 5 = 8

can anyone help with this .

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Source: Beat The GMAT — Data Sufficiency | Thu Jun 19, 2008 6:04 am

durgesh79: Master | Next Rank: 500 Posts; Posts: 167; Joined: Tue Apr 22, 2008 12:48 am; Thanked: 15 times

Re: please help

by durgesh79 » Thu Jun 19, 2008 6:15 am

anjaligeorge1 wrote:If a*b*c=60, where a, b, and c are integers greater than 1, a+b+c=?

(1) a+b=8
(2) Both a and b are odd numbers.

the answer says B .why cant it be D coz a ,b , & c can be 3 , 5 , & 4
as per statement 1 - a+ b : 3 + 5 = 8

can anyone help with this .

a,b,c could be 2,6,5 also .... thats why A is not suff.

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ildude02: Master | Next Rank: 500 Posts; Posts: 320; Joined: Sun Jan 13, 2008 10:00 pm; Thanked: 10 times

by ildude02 » Thu Jun 19, 2008 11:01 am

An other way of solving this is, we know that the prime factors of 60 = 2 x 2 x 3 x 5. Considering statement 1, a+ b = even , so a and b must be odd or a and b must be even. So a and b can 5 and 3 if odd, or they can 2 and 6 when considering even. So we know a+b+c can vary and is INSUFF.

Statement 2: clearly says a and b are odd and the two of the prime factors are odd as well3, 5). The other number C can only be 4. So there is only one value of a+b+c.