Edmund works at a constant rate and assembles 18 clocks in 3

Question

Edmund works at a constant rate and assembles 18 clocks in 3 hours. How much less time would be needed to assemble the same number of clocks if Edmund and Heinrich were working simultaneously?

1) Both Edmund and Heinrich assemble the same number of clocks every hour.

2) It takes Edmund and Heinrich, working simultaneously, half as long to assemble the clocks as it takes Heinrich working alone.


Can somebody please explain statement 2 to me?? I.e., how would I check whether statement 2 is sufficient?

M8 · Answer

1) is sufficient. 
2) is insufficient as we do not know the rate at which Heinrich works.

The answer is 'A'. But not sure.

Professor · Answer

given that Ed can assemble 18 clocks in 3 hours.
he/she can assemble 6 clocks in 1 hours.

from i, Ed and H can assembles the same no of clocks every hour. 
this means H can assembles 18 clocks in 3 hours. 
so working togather it takes 18/(6x2) = 3/2 hours hours to make 18 clocks. so suff...............

from ii, if it takes Edmund and Heinrich, working simultaneously, half as long to assemble the clocks as it takes (3/2) Heinrich working alone.

this statement is the same as above. it takes 3/2 hours to assemble 18 clocks. it takes 3/2 hours less time to do so. this is also suffffff........

chiragr · Answer

One simple way to look at 2nd is if Edmund and Heinrich work simultaniously they will finish 18 clock(work) in 1.5 hour 

and we know edmund takes 3 hour for 18 clock so required answer is 1.5 hour, so second is sufficient.

--------------------------------------------------------
Other way is to understand concept, how to derive and use euqation.

Work = Rate * Time

We = Re*Te
Wh = Rh*Th

total work Wt= Rt*Tt

Normally in such question work is same so We=Wh = Wt 

More over when two people work togather their rate will add up so..
Rt= Re+Rh
Wt/Tt = Wh/Th+We/Te

as We=Wh=Wt
 1/Tt = 1/Te + 1/Th 

and lot of time we take unit work so 
1= RtTt so 
Rt=1/Tt = 1/ 

 Rt = Th*Te/(Th+Te) 

I above two equation frequently to solve many problems.

remgeo · Answer

I'll go with A. 

2 is not sufficient because we know only Edmund's working pattern, not Heinrisch's.

jcgoodchild · Answer

Definitely D. 

We must remember the equation that work = rate * time. When multiple people work together, we add their rates. 


Statement 1: From this we know that their rates are equal. Therefore each has a clock building rate of 18/3 clocks per hour. Add, we get 12 clocks per hour. To build 18 clocks would take 1.5 hours, which is 1.5 hours less.


Statement 2: Remembering that we add the respective rates of work, we know that if the combined rate produces 18 clocks in 1.5 hours, the combined rate is 18/1.5, or 36/3, OR 12. We know Edmund's rate to be 18/3, so subtracting that from 36/3, we know that Heinrich's rate must be 18/3 as well.

Matador · Answer

OA is D.

See explanations above.

Edmund works at a constant rate and assembles 18 clocks in 3

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