Question 1044056
.
Frank can build a fence in twice the time it would take Sandy. Working together, they can build it in 7 hrs. 
How long will it take each if them to do it alone?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


<pre>
{{{1/F + 1/S}}} = {{{1/7}}},        (1)
F = 2S.            (2)

--->

{{{1/F + 1/(2F)}}} = {{{1/7}}},  --->  {{{3/(2F)}}} = {{{1/7}}}  --->  F = {{{(3*7)/2}}} = {{{21/2}}} = {{{10}}}{{{1/2}}} hours is the time for Frank.

Then the time for Sandy is {{{21/4}}} = {{{5}}}{{{1/4}}} hours.

<U>Answer</U>.  {{{10}}}{{{1/2}}} hours is the time for Frank;  {{{21/4}}} = {{{5}}}{{{1/4}}} hours is the time for Sandy.
</pre>

For details on how to solve joint work problems see the lesson

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Word-problems-WORKING-TOGETHER-by-Fractions.lesson>Using Fractions to solve word problems on joint work</A>,

in this site.