SOLUTION: I still can't get how to answer this question: If a girl works for 8 minutes and her brother works for 15 minutes, they can wash the front windows of their house. Also, if the gir

Question 156820: I still can't get how to answer this question:
If a girl works for 8 minutes and her brother works for 15 minutes, they can wash the front windows of their house. Also, if the girl works for 12 minutes and her brother works for 10 minutes, they can wash the same windows. How long will it take each person alone to wash windows? (Hint: if it takes t minutes for a person to do a job alone, then in 1 minute, the person can do 1/t of the job.)
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
f a girl works for 8 minutes and her brother works for 15 minutes, they can wash the front windows of their house. Also, if the girl works for 12 minutes and her brother works for 10 minutes, they can wash the same windows. How long will it take each person alone to wash windows?
:
Write two equations and use elimination
Let the completed job = 1
:
+ = 1
+ = 1
:
Multiply the 1st equation by 2, and the 2nd equation by 3:
Subtract the 1st equation from the 2nd
:
+ = 3
+ = 2
--------------------subtraction eliminates b
+ 0 = 1
g = 20 min, girl alone
:
Find b using the 1st equation:
+ = 1
Mult equation by 20b
8b + 20(15) = 20b
300 = 20b - 8b
12b = 300
b =
b = 25 min, boy alone
:
:
Check solution in the 2nd equation
+ =
+ = 1

RELATED QUESTIONS
If a girl works for 8 min. and her brother works for 15 min, they can wash the front... (answered by stanbon)

if a girl works for 8mins and her brother works for 15mins, they can wash the front... (answered by lwsshak3)

Bill and Marie create posters. They can complete a poster if Bill works for 24 minutes on (answered by richwmiller)

Dear Tutor, Could you help me find a answer to the following question. I would like... (answered by bucky)

Nick, Kevin, and Joe can paint a room in 1 hour 20 minutes if the work together. Working (answered by josgarithmetic)

Janet can wax her car in 8 hours. When she works together with Darlene, they can wax the... (answered by josmiceli)

candice rakes leaves for her neighbors. She charges $4 per hour to rake leaves plus $7 to (answered by fcabanski)

Mike can assemble a computer table in 40 minutes and I can do it in 60 minutes. If Mike... (answered by ptaylor)

Mike can assemble a computer table in 40 minutes and I can do it in 60 minutes. If Mike... (answered by ankor@dixie-net.com)