Working together, Jose and Jane can complete an assigned task in 20 days. However, if Jose worked alone and complete half the work and then Jane takes over the task and completes the second half of the task, the task will be completed in 45 days. How long will Jose take to complete the task if he worked alone? Assume that Jane is more efficient than Jose.
25 days
30 days
60 days
65 days
36 days
The first statement says x + y = 20
The second statement says x + y/2 = 45, or x + y = 90
You're supposed to set up the problem by deriving the rate from the first equation and substituting for the variables in the second equation (it looks like this: 1/90-y + 1/y = 1/20) You'll arrive at 60 and 30, which would make choice C the correct answer...BUT
I don't understand why you can't arrive at the answer the following way:
1/20-y + 1/y = 1/90
If you set up the equation this way instead of the correct way you will get the entire question wrong. Can someone PLEASE explain to me why that equation is wrong??? I"ve been trying to figure it out for a long time now and I just can't see why that equation could not be correct...
25 days
30 days
60 days
65 days
36 days
The first statement says x + y = 20
The second statement says x + y/2 = 45, or x + y = 90
You're supposed to set up the problem by deriving the rate from the first equation and substituting for the variables in the second equation (it looks like this: 1/90-y + 1/y = 1/20) You'll arrive at 60 and 30, which would make choice C the correct answer...BUT
I don't understand why you can't arrive at the answer the following way:
1/20-y + 1/y = 1/90
If you set up the equation this way instead of the correct way you will get the entire question wrong. Can someone PLEASE explain to me why that equation is wrong??? I"ve been trying to figure it out for a long time now and I just can't see why that equation could not be correct...
