is anyone good at maths and want 10 points?

Question

i have a mathmatical question need answering. to get the ten points you must give me the answer and how you worked it out:

a person can do a job in 3 hours, another person can do the same job in 4 hours, and yet another person can complete the job in 6 hours. if they all worked together how long would it take to complete the job?

first correct answer wins the 10 points.

Answer 1

1 hr 20 mins

A = 3 hours to do once
B = 4 hours to do once
C = 6 hours to do once

Lowest common denominator of 3, 4, 6 is 12
So in 12 hours

A does the job 4 times
B does the job 3 times
C does the job twice

In all in those 12 hours the three people have done the job 9 times.

On average to find out how long they took to do it once together;
12 divided by 9 = 1.3 [3 recurring]

1 hour 20 minutes

Answer 2

If a person does the job in three hours then he can do one-third of the job in an hour.

Likewise, the other two can do 1/4 and 1/6 of the job in one hour.

Working together they complete 1/3 + 1/4 + 1/6 = 3/4 of the job in one hour.

So they need 4/3 of an hour or 1 hour 20 minutes to complete the job.

Answer 3

The average time for the 3 of them to do the job is 3 + 4 + 6 =13 divided by 3 = 4 hrs and 20 minutes.
This is the average time for 1 of them to do the job. However as all three of them are doing it you need to divide this time by 3.
Which comes to 1 hour, 26 minutes and 40 seconds.

Answer 4

These are done by making a fraction for each person. If they're all working together for the same amount of time, each numerator is x. Their individual times go in the denominator. So this problem would look like

x/3 + x/4 + x/6 = 1

The 1 signifies the whole job being completed.

Multiply every term by the common denominator of 12.
4x + 3x + 2x = 12
9x = 12
x = 12/9 or 4/3 hours.

Answer 5

Okay in one hour

A=1/3=4/12
B=1/4=3/12
C=1/6=2/12

A+B+C=9/12=3/4

Therefore, in one hour, 3/4 of the work is finished. One quarter remains, which is 1/3 of what has been done. Therefore, the people need a third again of the time they have had

Therefore, the job can be done in 80 minutes (an hour and 20 minutes)

Answer 6

let t = time taken to do the job by the three working together

(t/3+t/4+t/6)= 1(hour) >>>>> 3t/4 = 1

>>>>>>>>>t= 1hour 20 minutes

therefore,it takes 1 hour and twenty minutes for the three to complete the job working together

Answer 7

In one hour the first person will do 1/3 of the job, second 1/4 and third 1/6
So in one hour 1/3+1/4+1/6=3/4 of total job will be done
so 75%:1=100%:x
x=100/75
x=4/3 hours
1 hour and 20 mins

Answer 8

Add 3+4+6
Divide the answer by 3
This gives your average.
I came out with 4 1/3 hours
Now find out how much 1/3 of an hour is:
Multiply 1/3 X 60 over 1
That gives you 60/3
Divide 3 into 60 (To find out minutes)
Your answer is 4 hours and twenty minutes.

Answer 9

I think the person doing the job in 3 hours is storing up problems for themselves. They will be expected to keep up this pace all the time, and will probably have a breakdown. If the 2 faster ones just sloweded down it would help - the job would be done when its done.

Answer 10

first

X can get 1 job done in 3 hours
Y can get 1 job done in 4 hours
Z can get 1 job done in 6 hours

amount of job done for persons X,Y,Z in t hours {t/3, t/4,t/6}

total amount of job done by all of X,Y,Z in t hours.

t/3 + t/4 + t/6

They got the job done, so

t/3 + t/4 + t/6 = 1

t(4*6) + t(3*6) + t(3*4) = 3*4*6

t =72/ (24 + 18 + 12) = 72/54 = 1.333333... = 1 hour 20 minutes.