Paula the painter had just enough paint for 30 identically sized rooms

Question

Paula the painter had just enough paint for 30 identically sized rooms. Unfortunately, on the way to work, three cans of paint fell off her truck, so she had only enough paint for 25 rooms. How many cans of paint did she use for the 25 rooms?

(A) 10
(B) 12
(C) 15
(D) 18
(E) 25

(A) 10
(B) 12
(C) 15
(D) 18
(E) 25

BrentGMATPrepNow · Answer

After Paula lost 3 cans of paint, she could paint 5 fewer rooms. 
So, it must take 3 cans of paint to paint 5 rooms.
This means, it must take 6 cans of paint to paint 10 rooms.
And 9 cans of paint to paint 15 rooms.
And 12 cans of paint to paint 20 rooms.
And 15 cans of paint to paint 25 rooms.

Answer: C

Cheers,
Brent

anbuKp · Answer

Let Paint required for 30 rooms = x;
Therefore Paint required for 1 room = x/30;

Paint required for 25 rooms = 25*(x/30) = (x-3) ; ('Since 3 cans were wasted) 
Solving for x => x= 18; For 25 rooms, x -3 = 15 cans

C

Archit3110 · Answer

solve linearly
cans per room ; 30/n
later after 3 are lost ; 25/n-3
since rate is same so
30/n= 25/n-3
n= 18 ; 30 rooms
3 cans fell so left 18-3 ; 15
IMO C

ScottTargetTestPrep · Answer

Let n = the total number of cans of paint for 30 rooms. We can create the proportion:

n/30 = (n - 3)/25

25n = 30(n - 3)

25n = 30n - 90

90 = 5n

n = 18

Since she used 3 fewer cans for 25 rooms, she used 15 cans of paint for the 25 rooms she painted.

Answer: C

Paula the painter had just enough paint for 30 identically sized rooms

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Paula the painter had just enough paint for 30 identically sized rooms

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