SOLUTION: twin brothers person a and person b, can mow their grandparents lawn together in 20 minutes. person a could mow the lawn by himself in 9 minutes or less time than it would take per

Question 932084: twin brothers person a and person b, can mow their grandparents lawn together in 20 minutes. person a could mow the lawn by himself in 9 minutes or less time than it would take person b. how long would it take person b to mow the lawn by himself?
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!
Set UP (per min KEY)
|Multiplying thru by 20b(b-9) so as all denominators = 1
....
20b + 20(b-9) = b(b-9)
b^2 - 49b + 180 = 0
(b-4)(b-45)= 0
b = 4, 45 (b= 4 cannot be used)
........
b = 45min and a would be 36min
.......
And checking
1/45 + 1/36 = 4/180 + 5/180 = 9/180 = 1/20

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