Fran can wash the car in 30 minutes. Gail can wash the car in 40 minutes.?

Question

Working together can they wash the car in less than 16 minutes?

Please include the work so I can understand thnx a lot!

Answer 1

If they work together to wash 1 car, here is the solution.

Simple math:
Fran = 30/2 = 15mins
Gail = 40/2 = 20mins
Working together, they can wash it in = (15+20)/2 = 35/2 = 17.5mins (this is theoritical).

Physics:
Fran = 1/30 car/min.
Gail = 1/40 car/min.
Together they wash at the rate of 1/30 + 1/40 car/min
therefore, 1/30 + 1/40=4/120+3/120=7/120 car/min.
1 car = 120/7 = 17.142857 minutes

Answer 2

Ask yourself what percent each could could complete per minute and add it
In 1 minute Fran can do 3.333%
Gail can do 2.5% in one minute
in 16 minutes the TOTAL for both possible is
(16 X 3.3333) PLUS ( 16 X 2.5 )
53% (Fran)+ 40% (Gail) that's 7% short of the whole car. Even at 17 Minutes you only have 99.2% of a clean car.

Answer 3

Another method. In 120 (the lowest common denominator) minutes Fran can wash 4 cars, Gail 3; making 7 happy owners. But there's only one owner, so we divide that 120 by 7, devoting 17.14etc minutes to that car.

Answer 4

fran washes at the rate of 1/30 car/min. gail washes at the rate of 1/40 car/min.

together they wash at the rate of 1/30 + 1/40 car/min
1/30 + 1/40=4/120+3/120=7/120 car per min.

1 car/(7/120) car/min=120/7 minutes=17.142857 minutes. The answer is NO.

Answer 5

Well : the total cars washed would be added 30+40=70 -16min
as shown here 70-16 = 54 cars per second for sub total !

Answer 6

Add 30 + 40 = 70
now divide by one half to get an average speed
of both girls working together.
Average speed would be 35.
Now you have 2 girls working at an average
speed of 35 minutes per girl.
Thus, you divide by 1/2 again.

answer = 17.5

Answer 7

1 / [(1/30) + (1/40)] = 17.14.

They can't wash it in less than 16 minutes

Answer 8

30/2=15
40/2=20
20+15=35
35/2=17.5