1. ## counting problem

All possible two factor products formed from the numbers 1,2,3,4.... 200. The number of factors out of the total obtained which are multiples of 5 is?

a. 5040
b. 7180
c. 8150
d. none of these

2. ## Re: counting problem

Originally Posted by swordfish774
All possible two factor products formed from the numbers 1,2,3,4.... 200. The number of factors out of the total obtained which are multiples of 5 is?
a. 5040
b. 7180
c. 8150
d. none of these
This is not a homework service. Please show what you have done.

3. ## Re: counting problem

hahaha!
I didnt understand the question, what does number of factors mean
non-multiples of 5 n 160 , multiples of 5 m 40 so, 160C1*40C1
and multiples of 5 n * muliples of 5 so 40C2

so 7180. but there is double counting, how do i remove that?

why do you say 'this is not a homework service'? i use it to solve doubts and verify answers.

4. ## Re: counting problem

Originally Posted by swordfish774
why do you say 'this is not a homework service'? i use it to solve doubts and verify answers.
When someone simply posts a list of problems with no comments, we assume that the person expects to get the answers just given to them.

5. ## Re: counting problem

okay, so can you please clarify the question? is the question about product of the factors? if yes then how do you go about it?
because 25*8= 5*40
this will lead to double counting..

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# all possible two factors products are formed from the no. 1,2,3,4....... 200. the number of products out of the total obtained which are multiple of 5 are

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