Question 548634
Let x = the number of hours to fill the pool.
The rate of filling for pipe A is {{{x/12}}} and for pipe B is {{{x/30}}}
The rate of filling for both A and B is:
{{{x/12+x/30 = 7x/60}}} so to fill the pool, set this equal to 1 and solve for x:
{{{7x/60 = 1}}} Multiply both sides by the multiplicative inverse of {{{7/60}}} which is{{{60/7}}} to get:
{{{x = 60/7}}}hours or
{{{x = 8}}}hours and {{{34.3}}}minutes.