An air conditioner can coo the hall in 40 miutes while another takes 45 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?  Choose the most appropriate option:
A) about 22 minutes
B) about 20 minutes
C) about 30 minutes
D) about 25 minutes
E) about 15 minutes
Take LCM of 40 and 45 = 360   40*9= 
<gadget id="calculator">40*9</gadget>
<output>360</output>
360 / 45*8=360.   So if both are switched on together , room cooled in 360/(8+9)=360/17=21.16 minutes   21.16 can be round to 22 minutes , so about 22 minutes   about 22 minutesNSWER:about 22 minutes
<result>A</result>
An air conditioner can coo the hall in 40 miutes while another takes 45 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?