# SAT question

• Aug 13th 2011, 06:37 AM
RK29
SAT question
All numbers divisible by both 4 and 15 are also divisible by which of the following?

A. 6
B. 8
C. 18
D. 24
E. 25

• Aug 13th 2011, 06:43 AM
e^(i*pi)
Re: SAT question
The LCM of 4 and 15 is 60.

So which of those numbers is a factor of 60?
• Aug 13th 2011, 06:46 AM
RK29
Re: SAT question
6 thanks, so if a number is factor of a LCM of two number, they can divide evenly multiples of those two number
Quote:

Originally Posted by e^(i*pi)
The LCM of 4 and 15 is 60.

So which of those numbers is a factor of 60?

• Aug 13th 2011, 07:29 AM
e^(i*pi)
Re: SAT question
Quote:

Originally Posted by RK29
6 thanks, so if a number is factor of a LCM of two number, they can divide evenly multiples of those two number

Yes, that's it exactly. It also holds for the LCM of more than two numbers.

For example the LCM of 2,3 and 8 is 24 so any other factor of 24 will divide by multiples of 2,3 and 8
• Aug 13th 2011, 08:05 AM
RK29
Re: SAT question
what's a quick way to find LCM and GCF? i am having hard time.
• Aug 13th 2011, 08:06 AM
e^(i*pi)
Re: SAT question
Quote:

Originally Posted by RK29
what's a quick way to find LCM and GCF? i am having hard time.

LCM and GCF

Prime factors are the easiest way, the link above explains it better than I can
• Aug 13th 2011, 08:10 AM
RK29
Re: SAT question
I learned that way when i was young, they complicated stuff over years