It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,

Question

It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate, how many hours will it take 8 cooks to bake 8 cakes?

A. 2 
B. 2.5
C. 3
D. 3.5
E. 4

I really can't solve this problem. I am having problem in approach.
Every time I see work problems I am stuck in approach.

In this question, I was approaching like 
 \frac{1}{4*4*4}

calculating the cakes baked by 1 cook in 1 hour. I don't even know if I am right.
but now I am stuck can anyone help me.

generis · Accepted Answer

WRTvariation.png The resources Bunuel listed are very helpful. I don't know exactly where you are lost. (No, you are not correct about individual rate, but you are very close!) There is one basic approach that might help. Use the standard RT=W formula, but add "number of workers" (or machines, etc.) to the left hand side of that formula. See the table above. It is a standard RTW table, but one column has been added: # of workers. We can manipulate RT=W. We can manipulate, exactly the same way, #*R*T = W First we need individual rate at which the bakers work, i.e. how many cakes per hour does an individual baker make? We get that rate from the first scenario. Then we use that rate to solve the second scenario. 1. Find individual rate from first scenario Manipulate the equation from above (# of workers) * r * t = W # of workers = 4 Rate = ?? Time = 4 Work = 4 Plugging into the formula: 4 * Rate * 4 = 4 Rate = \frac{4}{(4 * 4)} = \frac{1}{4} (The rate is in cakes/hour. ) 2. Use that individual baker rate, and manipulate the equation again for the second scenario. This time you need to find time. Basic equation once more is (# of workers) * r * t = W rate of individual worker = \frac{1}{4} # of workers = 8 Work = 8 Plugging into equation: 8 * \frac{1}{4} * time = 8 (\frac{8}{4})(Time) = 8 2*(Time) = 8 Time = 4 hours Hope that helps.

Bunuel · Answer

4 cooks take 4 hours to bake 4 cakes;
4*2 = 8 cooks will take 4/2 = 2 hours to bake 4 cakes;
8 cooks will take 2*2 = 4 hours to bake 4*2 = 8 cakes.

Or simply twice as many cooks will make twice as many cakes in the same amount of time.

17. Work/Rate Problems 
     Theory   
 Work Rate Problems - All in One Topic! 
 Work Word Problems Made Easy 
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Hope it helps.

prerakgoel03 · Answer

One word:-  AWESOME

manoj1115 · Answer

It takes 16 man-hours(4 cooks x 4 hours) for 4 cakes
So, it takes 16/4 man-hours for 1 cake

Now to make 8 cakes, we would need 8x4=32 man-hours
We already have 8 cooks with us, and so the number of hours these 8 cooks would need is 32/8=4 hours

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JeffTargetTestPrep · Answer

The rate of 4 cooks is 1 cake per hour. We can use a proportion to determine the rate of 8 cooks.

1/4 = x/8

x = 2

Since rate of 8 cooks is 2 cakes per hour, it will take 8/2 = 4 hours to bake 8 cakes.

Jashan79 · Answer

The time will remain the same. 
time taken by one cook to bake one cake is 4 hours 
4 cooks to bake 4 cakes = 4 hours 
8 cooks to bake 8 cakes = 4 hours

as the rate of a single cook is one cake in 4 hours.

sasyaharry · Answer

Unitary method will never fail you in these cases.

4 cooks - 4 cakes - 4 hours
1 cook - 1 cake -4 hours

At this point you can say, using logic, that 8 cooks will bake 8 cakes in 4 hours.

If it is not clear, continue to find:
1 cook bakes  \frac{1}{4}  of a cake - 1 hour. (this is the individual rate of one cook. In most cases you will benefit by finding the individual rate but not always)

For 8 cooks, the rate is  8*\frac{1}{4}  = 2

Now W=8 ; R = 2 and T =?
W=RT
T = 4 hours.

EMPOWERgmatRichC · Answer

Hi All,

When dealing with these types of rate questions, it helps to define the amount of 'work' needed to get to the end result.

Here, we're told that there are 4 cooks working 4 hours each... this means that there are 
(4 cooks)(4 hours each) = 16 hours of cook-time needed to make those 4 cakes.

By extension, each cake takes 16/4 = 4 hours of cook-time. Thus, to make 1 cake, you could have... 
1 cook work for 4 hours 
2 cooks work for 2 hours each 
4 cooks work for 1 hour each 
8 cooks work for 1/2 hour each. 
Etc.

We're asked how long it would take 8 cooks to make 8 cakes... Since each cake requires 4 hours of cook-time, it would take (8)(4) = 32 hours of cook-time to make those 8 cakes. With 8 cooks, that would be 32/8 = 4 hours each.

Final Answer:  4 hours

GMAT assassins aren't born, they're made, 
Rich

KanishkM · Answer

If i can get the rate of cook in an hour, i should be good.

4hrs for 4 cakes 
1 hr for 1 cake

Work = rate * time 
r = 1 cake /hr

1 cook = 1/4 cake /hr

Now 8 cooks will take 2 cake/hr

2 cakes in 1 hr 
4 cakes in 4 hrs

E

Archit3110 · Answer

4 cooks take 4 hours ; so 1 cook take 16 hours
and time taken to bake 4 cake ; 16/4 ; 4 hours per cook

so for 8 cooks to bake 8 cakes time required would be ;

total cake * no of hr per cake / no of cooks ; 8 * 4 /8 = 4 hours
IMO E

gokulvenkatesh · Answer

1. For 4 cakes, it is 4cooks*4hours = 16 cook-hours

2. For 8 cakes, it should be 32 cook-hours.

3. We have 8 cooks working for 8 cakes. so total time required will be 32/8 = 4 hours.

It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,

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It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,

Prep Toolkit

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