word problem

[smallsorrow]

On a staurday night, each of the rooms at a certain motel was rented for either 40$ or 60$. if 10 of the rooms that were rented for 60$ had instead be rented for 40$, then the total rent the motel charged for that night would have been reduced by 25%. what was the total rent the motel actually chraged for that night?

A) 600
B) 800
C) 1000
D) 1600
E) 2400


Does anyone have a fast way to solve this??

Thank you!

[schumi_gmat]

LEt the total rent br T and rooms for $40 be x and $60 by y.

T = 40x + 60 y
0.75 T = 40 (x+10) + 60 (y-10)

Solving, we get T = 800

[vishubn]

one more approach

question says ! if 10 rooms was charged 40$ instead of 60 ....
so this is a reduction of 20$/room so a loss of 200$
now 200$ represents 25% of the toal income loss ! then total income is 800$

Vishu

[stop@800]

simple soln

25% is 200$
so total 800