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 Post subject: Algebra Word ProblemPosted: Mon, 5 Dec 2011 05:31:35 UTC
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Joined: Mon, 5 Dec 2011 04:14:15 UTC
Posts: 1
I took an online Algebra quiz, and one of the problems states:

You start a cycling club and want to have every member recruit 3 new members at the end of each month. You are the only member of the club at the end of April, 2013. If your plan is carried out, how many members will be in the club at the end of:

May, 2013?
June, 2013?
July, 2013?
January, 2014?

I took the number of members at the end of each month and multiplied by 3, giving the answers:

May, 2013, 4
June, 2013, 12
July, 2013, 36
January, 2014, 26,244

After submitting the quiz, it said that was incorrect, and that the number of members at the end of each month should be multiplied by 4, giving the totals of:

May, 2013, 4
June, 2013, 16
July, 2013, 64
January, 2014, 26,2144

How is it correct to multiply by 4 when each member is recruiting 3 new members each month? I would like to understand this better for future reference.

Thank you!

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 Post subject: Re: Algebra Word ProblemPosted: Mon, 5 Dec 2011 05:35:43 UTC
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Joined: Wed, 30 Mar 2005 04:25:14 UTC
Posts: 12103
Location: Austin, TX
rex84 wrote:
I took an online Algebra quiz, and one of the problems states:

You start a cycling club and want to have every member recruit 3 new members at the end of each month. You are the only member of the club at the end of April, 2013. If your plan is carried out, how many members will be in the club at the end of:

May, 2013?
June, 2013?
July, 2013?
January, 2014?

I took the number of members at the end of each month and multiplied by 3, giving the answers:

May, 2013, 4
June, 2013, 12
July, 2013, 36
January, 2014, 26,244

After submitting the quiz, it said that was incorrect, and that the number of members at the end of each month should be multiplied by 4, giving the totals of:

May, 2013, 4
June, 2013, 16
July, 2013, 64
January, 2014, 26,2144

How is it correct to multiply by 4 when each member is recruiting 3 new members each month? I would like to understand this better for future reference.

Thank you!

You're not tripling the number of members, you're adding new members, so you need addition, not multiplication.

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 Post subject: Re: Algebra Word ProblemPosted: Tue, 6 Dec 2011 10:33:53 UTC
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Joined: Sun, 24 Jul 2005 20:12:39 UTC
Posts: 3692
Location: Ottawa Ontario
End Apr: 1
End May: 4
1*4 = 4

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 Post subject: Re: Algebra Word ProblemPosted: Tue, 6 Dec 2011 22:43:32 UTC
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Joined: Wed, 30 Mar 2005 04:25:14 UTC
Posts: 12103
Location: Austin, TX
alisabuckley08 wrote:
It is correct to multiply it by 4, since at the beginning you have recruited 3 members, and then each members will recruit another 3, adding themselves, will be 4 already that is why numbers are multiplied in 4 and not in 3. Hope that helps.

Yes, effectively 1 becomes 4 each time.

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