Two teams of interns are wrapping donated gifts at a hospital. if the teams work alone, team a can wrap all of the gifts in 7 hours, and team b can wrap all of the gifts in 5 hours. how many hours will it take the interns to wrap all of the gifts if both teams work together? round the answer to the nearest half hour.

Together it would take 3 hours.

Team A can wrap all gifts in 7 hours; thus they can wrap 1/7 of the gifts in 1 hour.

Team B can wrap all gifts in 5 hours; thus they can wrap 1/5 of the gifts in 1 hour.

1/7h + 1/5h = 1, where h is the number of hours; it equals 1 because it is 100% of the gifts;

Find a common denominator. 35 is the first thing 7 and 5 will both divide into. Convert the fractions:

5/35h + 7/35h = 1

12/35h = 1

Divide both sides by 12/35:

12/35h : 12/35 = 1 : 12/35

h = 1/1 : 12/35

h = 1/1 * 35/12

h = 35/12

h = 2.9

h ≈ 3