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Intern  Joined: 04 Sep 2017
Posts: 1
It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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5 00:00

Difficulty:   15% (low)

Question Stats: 56% (01:18) correct 44% (01:28) wrong based on 87 sessions

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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.
Senior SC Moderator V
Joined: 22 May 2016
Posts: 3574
Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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4
2
vishuboy wrote:
It takes 4 cooks 4 hours to bake 4 cakes. Assumingno change of rate, how many hours will it take 8 cooks to bake 8 cakes?

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.

Attachment: WRTvariation.png [ 17.23 KiB | Viewed 4993 times ]

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.
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General Discussion
Math Expert V
Joined: 02 Sep 2009
Posts: 58427
Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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1
1
vishuboy wrote:
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?

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.

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

For more check:
ALL YOU NEED FOR QUANT ! ! !
Ultimate GMAT Quantitative Megathread

Hope it helps.
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Intern  B
Joined: 05 Feb 2017
Posts: 39
Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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1
genxer123 wrote:
vishuboy wrote:
It takes 4 cooks 4 hours to bake 4 cakes. Assumingno change of rate, how many hours will it take 8 cooks to bake 8 cakes?

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.

Attachment:
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.

One word:- AWESOME
Intern  B
Joined: 13 Sep 2016
Posts: 10
Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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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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Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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vishuboy wrote:
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?

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.
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Intern  B
Joined: 10 Sep 2017
Posts: 8
Concentration: Operations, Organizational Behavior
Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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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.
Manager  S
Joined: 22 Nov 2016
Posts: 202
Location: United States
GPA: 3.4
Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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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.
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GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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1
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.

4 hours

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Director  G
Joined: 09 Mar 2018
Posts: 994
Location: India
Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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vishuboy wrote:
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

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
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Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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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

vishuboy wrote:
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.
Intern  B
Joined: 01 Feb 2018
Posts: 4
GMAT 1: 640 Q48 V30 Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,  [#permalink]

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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. Re: It takes 4 cooks 4 hours to bake 4 cakes. Assuming no change of rate,   [#permalink] 09 Feb 2019, 11:31
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