It takes 3hrs to paint a 24ft by 10ft wall. At the same rate how long will it take to paint a 16ft by 18ft wall.

Question

A) 3hr 6min

B) 3hr 36min

C) 3hr 48min

D) 4hr

Answer 1

3 : 240 :: t : 288    proportion 

240t = 3(288)        product means/extremes

 

Can you solve for t and answer?

Answer 2

my strategy is to use units to guide my expressions

 

square feet x     hours___  = hours  when we cancel "square feet"

                    square feet

 

the area of the first wall is 10 x 24 = 240 square feet

 

the rate to paint the wall is 240 square feet = 80 square feet 

                                           3 hours                    hours

 

the area of the second wall is 16 x 18 = 288 square feet

 

at the same rate,  288 square feet ÷ 80 square feet
                                                           hours

                        = 288 square feet x ____hours___    cancel square feet

                                                     80 square feet

                        = 288 hours

                             80

                        = 3.6 hours = 3 hours + 6/10 hours= 3 hours, 36 minutes