please help with this algebra word problem?

Question

ok so i know it seems easy and i think i got the answer
but i just need to double check it with u guys answers
thanks sooo much!


When each works alone Barbara can do a job in 15 hours less time than John. When they work together it takes them 10 hours to complete the job. How long does it take John working alone to do the job?

Answer 1

Let us assume that John can do the work in x hours while working alone.
Therefore working alone Barbara can do the work in x-15 hours
It takes them 10 hours to do the job while working together
Therefore,
10/x +10/(x-15)=1 {1 indicates the complete job]
Multiplying bth sides by x(x-15),we get
10x(x-15)/x
+10x(x-15)=x(x-15)
10(x-15)+10x=x^2-15x
10x-150+10x=x^2-15x
20x-150-x^2+15x=0
-x^2+35x-150=0
x^2-35x+150=0
(x-5)(x-30)=0
x=5 or 30rejecting x=5 as that will give the hours taken by Barbara to do the job a negative value,which is impossible,we get x=30
tHerefore Joh takes 30 hours to do the job alone

Answer 2

wait,
The answer should be 12 1/2 hours. Yes?
I think Britt did it correct but devided wrong...no???

Let x be John's time.
So Barbs will do it in x-15 hours.
So john abd Barbs working together will do job in
x+x-15
So x+x-15=10
2x-15=10
2x=10+15
x=25/2=12 1/2 hours.

Answer 3

How many hours does Barbara work? Maybe you forgot to add a part of the question. Im pretty good in algebra and am sure you are missing crucial information.

Answer 4

brittni's answer HAS TO BE WRONG--if John takes 15 hours longer than Barbara, according to her, she can do it in NEGATIVE time.

Answer 5

j+j-15=10
2j-15=10
2j=25
j=25/10 or 2 1/2

Answer 6

let x= John
let y= Barbara

x-15=y
x+y=10
x+(x-15)=10
2x-15=10
2x=25
x= 13.5
y=11.5