Question 403216
Add their rates to find the rate working together.
In words:
(1 wall / mason's time) + (apprentice's rate) = (1 wall/time working together)
Let {{{r[a]}}} = apprentice's rate of working
{{{1/15 + r[a] = 1/10}}}
{{{r[a] = 1/10 - 1/15}}}
{{{r[a] = 3/30 - 2/30}}}
{{{r[a] = 1/30}}}
The apprentice can construct 1 wall in 30 hours