Word equation again with fractions. Do I have this right?

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bradycat

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Howard can do a piece of work in 3.8 days and karl can do it in 7.1 days. How long will it take them to complete the job if they work together. Round the answer to the nearest 10th of a day.

so it's 1/3.8 = .26316

1/7.1 = .01409

total together is 0.40400 days
so it's 1/.40400 = 2.475 days?

Not sure what they mean by 10th of a day.
Do I have this right and if not please correct and explain. Thanks. Joanne
 
Hello, bradycat!

Don't use rounded-off decimals . . . It's very inaccurate.

Howard can do a piece of work in 3.8 days and Karl can do it in 7.1 days.
How long will it take them to complete the job if they work together.
(Round the answer to the nearest 10th of a day.)
Click to expand...

\(\displaystyle \text{Howard can do the job in }3.8 \:=\:\tfrac{38}{10} \:=\:\tfrac{19}{5}\text{days.}\)
\(\displaystyle \text{In one day, he can do: }\:\frac{1}{\frac{19}{5}} \:=\:\tfrac{5}{19}\text{ of the job.}\)
\(\displaystyle \text{In }x\text{ days, he can do: }\tfrac{5x}{19}\text{ of the job.}\)

\(\displaystyle \text{Karl can do the job in }7.1 \,=\,\tfrac{71}{10}\text{ days.}\)
\(\displaystyle \text{In one day, he can do: }\:\frac{1}{\frac{71}{10}} \:=\:\tfrac{10}{71}\text{ of the job.}\)
\(\displaystyle \text{In }x\text{ days, he does: }\tfrac{10x}{71}\text{ of the job.}\)

\(\displaystyle \text{Together, in }x\text{ days, they do: }\:\frac{5x}{19} + \frac{10x}{71}\text{ of the job.}\)

\(\displaystyle \text{But in }x\text{ days, they will have completed the job (1 job.)}\)


\(\displaystyle \text{There is our equation }\quad\hdots \quad \frac{5x}{19} + \frac{10x}{71} \;=\;1\)

 
My answer has to be in hours and rounded to the tenth of a day.

So what is the answer then?
 
bradycat said:
My answer has to be in hours and rounded to the tenth of a day.

So what is the answer then?
Click to expand...

First solve for 'x'.

What is the unit of 'x' - days or hours?
 
X is days as the question says the work they are doing are in days.

I tried to figure it out and I am lost. Going back to college is a tough one!

If you can help, thanks again
Joanne
 
Hello,
That does not help me solve it. if I don't get it it's not going to work.
I need the answer to see what I did wrong or try to figure it out.
J
 
bradycat said:
so it's 1/.40400 = 2.475 days?
Not sure what they mean by 10th of a day.
Click to expand...
That's correct Joanne; 2.4752293...
Nearest 10th woud be 2.5
 
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