Andrew M. answered • 03/11/16

Tutor

New to Wyzant
Mathematics - Algebra a Specialty / F.I.T. Grad - B.S. w/Honors

Adele arranges the library in 2.5 hours so she does

1/2.5 parts per hour or .4 parts per hour.

This can also be put in fractional terms

1/2.5 = 1/(2 1/2) = 1/(5/2) = 2/5 parts per hour

**A = 2/5 parts per hour**

Basically this says Adele could complete the job

2 times in 5 hours

Brother arranges the library in 4.5 hours so he does

1/4.5 parts per hour or = 2/9 parts per hour

**B = 2/9 parts per hour**

Basically this means he could complete the job

2 times in 9 hours

Letting x=# hours to do the work together it takes

x(A + B) = 100% or

x(2/5 + 2/9) = 1

x(18/45 + 10/45) = 1

x(28/45) = 1

x = 45/28 = 1 17/28 hours = 1.607 hours

Rounding to the nearest tenth it takes 1.6 hours

for Adele and her brother to arrange the library together.