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If 2 people are digging a hole in 5 hours then how many people does it take to dig a hole in 5 minutes?

For Grade 5 Math

Guest Mar 3, 2015

Best Answer 

 #2
avatar+91435 
+10

I always find these questions super tricky.

I am going to do it without algebra. :)

 

2 people   take   5hours

If you have more people, it would take less time - that makes sense doesn't it?

so

2*5people  take  5 ÷ 5 hours

10 people    take    1 hour

now 5 minutes is 5/60=1/12 of an hour

10*12 people would take  1/12 hours

120 people will take  5 minutes

 

Of course they would all get in each others way so I do not think it would really work that way.   LOL 

Melody  Mar 3, 2015
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4+0 Answers

 #1
avatar+80935 
+10

This is known as a "see-saw" problem.....that is, the product of one side of the equation must equal the product of the other side

So, two people dig a hole in 5 hrs. = 300 minutes

So

2 x 300  = N * 5    where N is the number of people we're looking for

600 = N * 5      divide by 5

120 = N   

So it takes 120 people to dig the same hole in 5 minutes

To see the logic of this, we need to dig the hole 60 times as fast......therefore....we need 60 times as many people....  and 60 x 2 = 120.....!!!

 

CPhill  Mar 3, 2015
 #2
avatar+91435 
+10
Best Answer

I always find these questions super tricky.

I am going to do it without algebra. :)

 

2 people   take   5hours

If you have more people, it would take less time - that makes sense doesn't it?

so

2*5people  take  5 ÷ 5 hours

10 people    take    1 hour

now 5 minutes is 5/60=1/12 of an hour

10*12 people would take  1/12 hours

120 people will take  5 minutes

 

Of course they would all get in each others way so I do not think it would really work that way.   LOL 

Melody  Mar 3, 2015
 #3
avatar+80935 
0

Well...that depends on how big the hole is.......maybe they're digging to China...LOL!!!

 

CPhill  Mar 3, 2015
 #4
avatar+91435 
0

well then the 120 of them had better get a wriggle on then.  :))

Melody  Mar 3, 2015

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