2009 AMC 10B Problem 3

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?

10

12

15

18

25

Losing

3

cans cost her exactly

5

rooms

The paint-per-room rate is

\dfrac{3}{5}

of a can

The lost

3

cans would have painted

30-25=5

rooms, so each room takes

\dfrac35

of a can.

For

25

rooms she used

\dfrac35\cdot25=15

cans.

Thus, the correct answer is C.

Problem 3 in other years