Question

Henry and Irene working together can wash all the windows of their house in 1h 48m. Working alone, it takes Henry 1.5 h more than Irene to do the job. How long does it take each person working alone to wash all the windows?
Please show equation.

Answer 1

Let the time it takes Irene to do the work alone be x, then
1/x + 1/(x + 1.5) = 1/1.8
1.8(x + 1.5 + x) = x(x + 1.5)
3.6x + 2.7 = x^2 + 1.5x
x^2 - 2.1x - 2.7 = 0
x = 3

Therefore, it takes Irene 3 hours and Henry 4.5 hours to do the work individually.