SOLUTION: mary joy can bake a cake in 2 hrs. Clarissa can do it in 4 hors. How long will it take them to bake a cake if they joined together

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Question 1168164: mary joy can bake a cake in 2 hrs. Clarissa can do it in 4 hors. How long will it take them to bake a cake if they joined together

Found 3 solutions by Boreal, ikleyn, josgarithmetic:
Answer by Boreal(15235)   (Show Source):
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in 1 hour, Joy makes (1/2) and in x hours (x/2)
Clarissa makes (x/4) in x hours
so (x/2)+(x/4)=1
multiply through by 4
2x+x=4
3x=4
x=(4/3) hour, the answer
Joy will make 2/3 of it and Clarissa will make 1/3

Answer by ikleyn(52784)   (Show Source):
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.

There are activities / (problems) where working in parallel (joint work) allows to reduce the completion time.

There are other activities / (problems) where working in parallel does not allow to reduce the completion time.

The common sense is given to Math problems composers to distinct between these different kinds of activities.

Answer by josgarithmetic(39617)   (Show Source):
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Do you expect that the time the dough or batter spends in the oven is any less due to two people baking it than if just one person baking it? No! The problem description is very poor as any kind of constant work rates example.