Question

You and your friend are painting the walls in your apartment. You estimate that there is 1000 square feet of space to be painted. You paint at a rate of 4 square feet per minute and your friend paint at a rate of 3 square feet per minute. Your friend shows up to help you paint 45 minutes after you've already started painting
a. Write an equation that gives the total number of square feet y as a function of the number of minutes X it takes to paint all the walls
b. How long will it take you and your friend finish painting? Round your answer to the nearest minute.

Answer 1

after 45 minutes you will have painted 4*45=180 square feet.

so the total number of painted area, y, is:

y=180+x*(3+4) after the 45 minutes

where x is the number of minutes AFTER THE 45 minutes:

if y is 1000 then

1000=180+x*7
820=x*7
x=117.14

so 117 minutes, or one hour and 57 minutes.