Bob can mow a lawn in 5 hours. John can mow the same lawn in 3. If done together how long will it take?

Answer 1

Let us assume that they can mow it in x hours while working together
therefore,
x/5 +x/3 =1 (the whole work)
or3x+5x=15 [multiplying both sides by 15]
or 8x=15
or x=15/8 hrs=1 7/8 hrs=1 hr 52 m 30 sec
Hence they take 1 hr 52m 30 sec to do the work working together

Answer 2

Let area of lawn = A m²
Bob cuts A / 5 m² in 1 hour
John cuts A / 3 m² in 1 hour
Working together they will cut
A / 5 + A / 3 m² in 1 hour
3A / 15 + 5A / 15 m² = 8 A /15 m² in 1 hour
working together, the time is given by:-
Time = Area / rate of work
t = A / [ 8 A / 15 ] h
t = 15 / 8 h
t = 1 7/8 hours
t = 1 h 52.5 min

Answer 3

in 1 hour bob can mow 1/5th part of the lawn and john can mow 1/3rd. so they can mow together (1/5 + 1/3) or 8/15 part of the lawn in 1hour.
so they together can mow the complete lawn in 1/(8/15) or 15/8hours.that is approximately 2 hours.

Answer 4

15 / 8 hours = 1 hour, 52 minutes, 30 seconds.

I know you are expected to get involved in fractional reciprocals on this one, but this formula is so much faster and easier : Product over sum = together.

So I just did (5 x 3) / (5 + 3) = 15 / 8
Then I turned 7 / 8 of an hour into minutes and seconds like this : (7 x 60) / 8 = 420 / 8 = 52 1/2 minutes.
And 1/2 a minute is 30 seconds, so the answer is 1 hour, 52 minutes, and 30 seconds

Answer 5

in 1hr, Bob can mow 1/5 of the lawn and John can mow 1/3 of the lawn

let t be the time it takes both of them to finish the lawn
(1/5)t + (1/3)t = 1
(8/15)t = 1
t = 1.875 hr

Answer 6

The answer is 1.467 hours. Here's how you do it:
In one hour, Bob can do 1/5 of the job, or 3/15. In one hour, John can do 1/3, or 5/15. In one hour, they can do 8/15 of the job together. So, they need 1 and 7/15 hours to complete the entire task, which is 1.467 hours

Answer 7

Let x = no. of hours to finish a job.

Equation:
x/3 + x/5 = 1
5x/15 + 3x/15 = 1
8x/15 = 1
8x = 1 * 15
x = 15/8 hr or 1 7/8 hrs or 1 hr, 52 min, 30 sec

Answer 8

5*3/(5+3) = 15/8 = 1 7/8 hours

Answer 9

It is simple
(5+3)/2=4 ans

Answer 10

It depends, they could be a bunch of nitwits and keep running into eachother.

I do however know how to solve it, but if you dont learn that yourself, you'll turn into Bob and John.