Question

An air conditioner can cool the hall in 40 minutes 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? (a) About 22 minutes (b) About 20 minutes (c) About 30 minutes (d) About 25 minutes

Answer 1

i think its about 20 minutes...

Answer 2

Answer:22 minutes

Step-by-step explanation:

first air conditioner cool in 45 minutes

so in 1 minute work is=$\frac{1}{45}$

similarly, for second air conditioner 1 minute work is =$\frac{1}{40}$

let both will cool in x minutes.

so

$\frac{1}{40}+\frac{1}{45}=\frac{1}{x}\\\\\frac{9+8}{360}=\frac{1}{x}\\\\\frac{17}{360}=\frac{1}{x}\\\\x=21\tfrac{3}{17}$

x≅22

so both will cool the room in 22 minutes.