by d. fisher. copyright notice: all of the images used in this presentation are from the internet...
TRANSCRIPT
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Marge can clean the house in 3 hrs. Lisa can clean it in 5 hrs.
How long will it take them to clean the house if they both work together?
Bart can wash the car in 20 min.Homer can wash it in 30 min.How long will it take them to wash the car if they both work together?
Mr. Skinner can enroll 15 students per hr.
Mr. Chalmer can enroll 20 students per hr.
How long will it take them to enroll 140 students working together?
Minutes work better than hours.
Mr. Skinner enrolls 15 students per 60 min.,
so he enrolls 15/60 or 1/4 students per min.
Minutes work better than hours.
Mr. Chalmer enrolls 20 students per 60 min.,
so he enrolls 20/60 or 1/3 students per min.
Mrs. Krabappel can grade a set of papers in 11/2 hrs.
Miss Hoover can grade them in 80 min.
How long will it take them to grade one set if they both work together?
1/90M + 1/80M = 3
720(1/90M + 1/80M) = 720(3)
8M + 9M = 2160
17M = 2160
M = 1271/17 min. A little more than 2 hrs.