heshamelaziry wrote:which of the following represents the fraction of the job that B will not have to complete?

Is it "B will have to complete" in the qn? In that case, E makes sense

papgust wrote:

heshamelaziry wrote:which of the following represents the fraction of the job that B will not have to complete?

Is it "B will have to complete" in the qn? In that case, E makes sense

Please provide explanation.

I guess i misunderstood the question. Agree that the question is worded fine.

A takes x hrs
B takes y hrs

Together, (x+y)/xy job

Qn says fraction of a job B will NOT have to complete - This means that it refers to job done by A.

Therefore, fraction of job done by A will be (1/x)/[(x+y)/xy] ==> (1/x)*(xy/x+y)

Therefore, answer is y/x+y. Hope my approach is fine.

papgust wrote:I guess i misunderstood the question. Agree that the question is worded fine.

A takes x hrs
B takes y hrs

Together, (x+y)/xy job

Qn says fraction of a job B will NOT have to complete - This means that it refers to job done by A.

Therefore, fraction of job done by A will be (1/x)/[(x+y)/xy] ==> (1/x)*(xy/x+y)

Therefore, answer is y/x+y. Hope my approach is fine.

I hope you can be patient with me . If B does y then seems to me that B fraction of the job is y/y+x so B fraction of the job that it does NOT do is A part of the job that it does, then it should be x/x+y !!!!

I don't know what I am missing !!!!

heshamelaziry wrote: I hope you can be patient with me . If B does y then seems to me that B fraction of the job is y/y+x so B fraction of the job that it does NOT do is A part of the job that it does, then it should be x/x+y !!!!

I don't know what I am missing !!!!

Fraction that B does is not as you describe. Fraction of JOB is like Distance =RatexTime. The rate is 1/x and 1/y. Distance = job, or 1. Therefore, the portion completed by B in a unit of time is 1/y, likewise the portion done by A is 1/x. The fraction of the whole job done by B is 1/y/(1/x)+(1/y), or x/(x+y)

Bah, don't know if this is right but I just did it by:

X= 1 hour
Y= 1 hour

It will take them 1/2 hour to complete it together, so Y only needs to do half as much work as normal.

I then just plugged in until E where y/(x+y) was 1/2, which got me the answer.

However, I'm sure an expert can tell you how to get it without plugging in much faster

Ludacrispat26 wrote:Bah, don't know if this is right but I just did it by:

X= 1 hour
Y= 1 hour

It will take them 1/2 hour to complete it together, so Y only needs to do half as much work as normal.

I then just plugged in until E where y/(x+y) was 1/2, which got me the answer.

However, I'm sure an expert can tell you how to get it without plugging in much faster

This turned out to be simple work problem; if there were numbers, it would have been clear. I saw this question with numbers, but solved differently, and so got confused. Also, i got tricked by the part that machine B does not do.

say A = 2 , B = 3----> 1/2 + 1/3 = 5/6----> take reciprocal of 5/6 to get time taken if both work together.
Now, the fraction of the job that machine B does not do is that fraction of the job that machine A does. So, (1/2) / (5/6) = something

heshamelaziry wrote:

papgust wrote:I guess i misunderstood the question. Agree that the question is worded fine.

A takes x hrs
B takes y hrs

Together, (x+y)/xy job

Qn says fraction of a job B will NOT have to complete - This means that it refers to job done by A.

Therefore, fraction of job done by A will be (1/x)/[(x+y)/xy] ==> (1/x)*(xy/x+y)

Therefore, answer is y/x+y. Hope my approach is fine.

I hope you can be patient with me . If B does y then seems to me that B fraction of the job is y/y+x so B fraction of the job that it does NOT do is A part of the job that it does, then it should be x/x+y !!!!

I don't know what I am missing !!!!

As i mentioned this will be the formula

Fraction of job done by A will be (1/x)/[(x+y)/xy] ==> (1/x)*(xy/x+y)

x gets cancelled out for the job done by A resulting in y/x+y