An air conditioner can coo the hall in 20 minutes while another takes 25 minutes to cool under similar conditions. if both air conditioners are switched on at same instance then how long will it take to cool the room?
Answers.
A) about 14 minutes
B) about 12 minutes
C) about 15 minutes
D) about 16 minutes
E) about 17 minutes
Take LCM of 20 and 25 = 100   20*5= 
<gadget id="calculator">20*5</gadget>
<output>100</output>
100/ 25*4=100.   So if both are switched on together , room cooled in 100/(5+4)=100/9=11.11 minutes   11.11 can be round to 12 minutes , so about 12 minutes   ANSWER: about 12 minutes
<result>B</result>
An air conditioner can coo the hall in 20 minutes while another takes 25 minutes to cool under similar conditions. if both air conditioners are switched on at same instance then how long will it take to cool the room?