It takes Avery 5 hours to build a brick wall while Tom can do it in 4 hours. If the two start working together and after an hour Avery leaves, how much time will it take Tom to complete the wall on his own? Choose the correct answer
A) 1 hour and 20 minutes.  B) 2 hours and 12 minutes.  C) 1 hour and 40 minutes.  D) 55 minutes  E) 2 hours and 20 minutes
Avery's efficiency is 100/5= 
<gadget id="calculator">100/5</gadget>
<output>20</output>
20%   Tom's= 100/4= 
<gadget id="calculator">100/4</gadget>
<output>25</output>
25%   they worked together for 1 hour and finished 45% of the job   remaining= 55 %   Tom will complete 25% in 60 minutes , 50% in 120 minutes and ,   5% in   60*5/25= 
<gadget id="calculator">  60*5/25</gadget>
<output>12</output>
12 minutes   time taken by Tom to finish the remaining on his own= 120+12= 
<gadget id="calculator">120+12</gadget>
<output>132</output>
132 minutes   ANSWER:2 hours and 12 minutes.
<result>B</result>
It takes Avery 5 hours to build a brick wall while Tom can do it in 4 hours. If the two start working together and after an hour Avery leaves, how much time will it take Tom to complete the wall on his own?