Together they can paint the wall in x minutes. Working together, in 1 minute, they do 1/x of the job.
The student who paints the wall in 16 minutes does 1/16 of the job in 1 minute. The student who paints the wall in 24 minutes does 1/24 of the job in 1 minute. Together, they do 1/16 + 1/24 of the job in 1 minute, but from above, we see that together, they do 1/x of the job in 1 minute, so 1/16 + 1/24 must equal 1/x. That gives us our equation.
1/16 + 1/24 = 1/x
1/16 * 3/3 + 1/24 * 2/2 = 1/x
3/48 + 2/48 = 1/x
5/48 = 1/x
x = 48/5 = 9.6
Answer: It takes them 9.6 minutes, or about 10 minutes to do the job together.
