Question 198837
Given:
Jill's rate of building: (1 dog house) / (4 hours)
Todd's rate of building: (1 dog house) / (6 hours)
Let {{{t}}} = time to build 1 dog house working together
Add their rates to get rate with both working together
{{{1/4 + 1/6 = 1/t}}}
{{{3/12 + 2/12 = 1/t}}}
Multiply both sides by {{{12t}}}
{{{3t + 2t = 12}}}
{{{5t = 12}}}
{{{t = 2.4}}}
It will take them 2.4 hours working together