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July 4th, 2011, 11:08 AM  #1 
Member Joined: Jul 2011 Posts: 46 Thanks: 0  ten boys can rob 30
Sir, please sir, I'm asking really because I don't know to solve: ten boys can rob 30 shops in 60 days. In how many days 5 boys can rob 15 shops? 
July 4th, 2011, 12:54 PM  #2 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,155 Thanks: 462 Math Focus: Calculus/ODEs  Re: ten boys can rob 30
Perhaps the simplest way to answer this is to observe that since both the number of boys and number of shops is divided by 2, the number of days would remain the same.

July 4th, 2011, 03:26 PM  #3 
Member Joined: Jul 2011 Posts: 46 Thanks: 0  Re: ten boys can rob 30
Thanks Mark, I understand.

July 5th, 2011, 05:04 AM  #4 
Member Joined: Jul 2011 Posts: 46 Thanks: 0  Re: ten boys can rob 30
sir sorry sir i think here my concept is not clear sir can you please tell me how to solve this sir sorry

July 5th, 2011, 10:06 AM  #5 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,155 Thanks: 462 Math Focus: Calculus/ODEs  Re: ten boys can rob 30
If 10 boys can rob 30 shops in 60 days, then (assuming each boy does an equal amount of robbing at a constant rate) each boy robs 1 shop every 20 days. So, 5 boys will rob 5 shops every 20 days, and thus 5 boys will rob 3·5 = 15 shops in 3·20 = 60 days. Or, you can say 1 boy robs 3 shops every 60 days, thus 1·5 = 5 boys rob 3·5 = 15 shops every 60 days. 

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