confused one

This topic has expert replies
Senior | Next Rank: 100 Posts
Posts: 66
Joined: Tue Jun 05, 2007 1:39 pm
Thanked: 1 times

confused one

by hakyology » Mon Jul 07, 2008 7:15 am
On a Saturday 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 been rented for $40, then the total rent the motel charged for that night would have been reduced by 25 percent. What was the totla rent the motel actually charged for that night?

A)$600
B)$800
C)$1,000
D)$1,600
E)$2,400


Please explain.

The answer is B.

I got $850 where it is not there among the answer choices.
Source: — Problem Solving |

Master | Next Rank: 500 Posts
Posts: 135
Joined: Mon Jun 23, 2008 3:56 am
Thanked: 7 times

by sethids » Mon Jul 07, 2008 7:26 am
x = No. of rooms rented for $40
y = No. of rooms rented for $60

We need to find the value of 40x + 60y which is the total value of the rooms rented on the particular night.

deducing the equation from given information:
(40x + 60y)*3/4 = 40(x + 10) + 60(y - 10)
=> 120x + 180y = 160x + 1600 + 240y - 2400

simplifying on both sides we get:
40x + 60y = 800.

Hence B is the answer.

Newbie | Next Rank: 10 Posts
Posts: 6
Joined: Mon Apr 21, 2008 3:16 am

by kanak » Mon Jul 07, 2008 7:34 am
Yes. The ans is B. Here's how:

Let there be x other rooms apart from the 10 rooms.

10 rooms @ $60 = $600
Rest of the rooms (i.e., x) @ $40 = 40x

600 + 40x is the cost.

If 10 rooms had $40 as rent = $400
Rest of the rooms = 40x

400 + 40x is the alternative cost.

600 + 40x = T
400 + 40x = (3/4) T

solve for T and you'll get
T = 800.

Senior | Next Rank: 100 Posts
Posts: 66
Joined: Tue Jun 05, 2007 1:39 pm
Thanked: 1 times

by hakyology » Mon Jul 07, 2008 7:36 am
hm...i do not get that. could you explain further? thanks.

Newbie | Next Rank: 10 Posts
Posts: 1
Joined: Sun Jun 08, 2008 9:36 am
Thanked: 1 times

=

by Robertogmat » Tue Jul 08, 2008 2:11 pm
hakyology wrote:hm...i do not get that. could you explain further? thanks.
another way to solve it:

If the hotel had rented the 10 rooms for Usd 40 instead of usd 60, it would have lost USd 20 * 10 rooms = Usd200

Usd 200 corresponds to the reduction of 25%.
therefore:

0.25x=200
x=800

User avatar
Master | Next Rank: 500 Posts
Posts: 228
Joined: Sun Jun 29, 2008 8:47 pm
Thanked: 15 times
Followed by:1 members

by amitdgr » Wed Jul 09, 2008 2:40 am
To find => total cost = x

"If 10 of the rooms that were rented for $60 had instead been rented for $40"

i.e. instead of charging 60*10 for ten rooms, if they had charged 40*10

"then the total rent the motel charged for that night would have been reduced by 25 percent"

i.e. the rent lost = (60*10) - (40*10) = 200 is actually 25% of x

put into equation , 200 = 0.25x

=> x= USD 800

HTH

Amit

User avatar
Master | Next Rank: 500 Posts
Posts: 228
Joined: Sun Jun 29, 2008 8:47 pm
Thanked: 15 times
Followed by:1 members

Re: confused one

by amitdgr » Wed Jul 09, 2008 3:32 am
hakyology wrote:
I got $850 where it is not there among the answer choices.
Can you explain the method you tried ? So that we can find out where you went wrong. Might help us to avoid any such mistake in the future.


Amit

User avatar
Legendary Member
Posts: 566
Joined: Fri Jan 04, 2008 11:01 am
Location: Philadelphia
Thanked: 31 times
GMAT Score:640

by AleksandrM » Wed Jul 09, 2008 9:50 am
Hey, how come you can't solve this problem using the following equation?

(40y + 600) - (40y + 400)/ 40y + 600 = .25

You would end up with y = 35

Then you had a rent of 40(35) + 600 = 2000

But instead you had 40(35) + 400 = 1800

User avatar
Legendary Member
Posts: 566
Joined: Fri Jan 04, 2008 11:01 am
Location: Philadelphia
Thanked: 31 times
GMAT Score:640

by AleksandrM » Wed Jul 09, 2008 9:55 am
Never mind. I see my mistake. Instead of making the first figure R for total rent and second 3/4R for the reduced rent, I made them both R.