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Wendy, Yvonne, and Elizabeth are baking cookies for a bake sale. Wendy

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Wendy, Yvonne, and Elizabeth are baking cookies for a bake sale. Wendy  [#permalink]

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New post 01 Nov 2018, 00:48
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

83% (02:15) correct 17% (02:38) wrong based on 27 sessions

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Wendy, Yvonne, and Elizabeth are baking cookies for a bake sale. Wendy can bake all of the cookies in 10 hours, Yvonne can bake half of the cookies in 3 hours, and Elizabeth can bake a third of the cookies in 5 hours. If Wendy and Elizabeth bake for 2 hours, how long will it take Yvonne to finish baking the rest of the cookies?

A. 1.8
B. 2
C. 3
D. 3.6
E. 4

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Re: Wendy, Yvonne, and Elizabeth are baking cookies for a bake sale. Wendy  [#permalink]

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New post 01 Nov 2018, 01:29
1
W does 1/10 work in 1 hour
Y does 1/6 work in 1 hour
E does 1/15 work in 1 hour
In 2 hour W & E does 2*(1/10 + 1/15) = 2/6 work
Y takes (4/6) / (1/6) = 4 hour
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Re: Wendy, Yvonne, and Elizabeth are baking cookies for a bake sale. Wendy  [#permalink]

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New post 01 Nov 2018, 01:50
Bunuel wrote:
Wendy, Yvonne, and Elizabeth are baking cookies for a bake sale. Wendy can bake all of the cookies in 10 hours, Yvonne can bake half of the cookies in 3 hours, and Elizabeth can bake a third of the cookies in 5 hours. If Wendy and Elizabeth bake for 2 hours, how long will it take Yvonne to finish baking the rest of the cookies?

A. 1.8
B. 2
C. 3
D. 3.6
E. 4


W, Y and E are baking cookies at different rates. W & E bake cookies for two hours, how long would Y take to bake the rest of the cookies? is the question.

In one hour W bakes 1/10th of cookies.

E can bakes all the cookies in 15 hours.
In one hour E bakes 1/15th of cookies.

Working together for two hours,

In one hour, W + E = 1/10 + 1/ 15 = 5 / 30 = 1/6 of the cookies.

In two, 1/3rd of the cookies are baked.

So Y needs to come in and bake 2/3rd of the cookies.

She takes 3 hours to bake 1/2 the cookies

So she takes 6 hours for all the cookies and 2/3rd of that to bake 2/3rd of the cookies... or 2/3 * 6 = 4 hours.

Hence Option (E) is our choice.

Best,
Gladi
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Re: Wendy, Yvonne, and Elizabeth are baking cookies for a bake sale. Wendy   [#permalink] 01 Nov 2018, 01:50
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Wendy, Yvonne, and Elizabeth are baking cookies for a bake sale. Wendy

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