SOLUTION: Sara wants to paint the wood around 4 windows in her house. She thinks that she can paint each window in 90% of the time it took to paint the previous window. If it takes her 30 mi

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: Sara wants to paint the wood around 4 windows in her house. She thinks that she can paint each window in 90% of the time it took to paint the previous window. If it takes her 30 mi      Log On


   

Question 938373: Sara wants to paint the wood around 4 windows in her house. She thinks that she can paint each window in 90% of the time it took to paint the previous window. If it takes her 30 minutes to paint the first window, how long will it take to paint all 4 windows. Please help me to solve this kind of math problem thanks in advance )))
Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!
30 minutes for the 1st window

PLUS

90% of 30 minutes = .90(30) = 27 minutes for the 2nd window

PLUS

90% of 27 minutes = .90(27) = 24.3 minutes for the 3rd window

PLUS

90% of 24.3 minutes = .90(24.3) = 21.87 minutes for the 3rd window.

Add them up: 

 30
 27
 24.3
 21.87
------
103.17

Divide that by 60

     1.7195
  --------- 
60)103.1700
    60
   ---
    43 1
    42 0
    ----
     1 17
       60
     ----
       570
       540
       ----
        300
        300
        ---

Multiply 0.7195 by 60, get 43.17

1 hour 43.17 minutes

Edwin