Three types of pencils, J,K, and L, cost $0.05, $0.10, and $0.25 each, respectively. If a box of 32 of these pencils costs a total of $3.40 and if there are twice as many K pencils as L pencils in the box, how many J pencils are in the box?

(A) 6
(B) 12
(C) 14
(D) 18
(E) 20

Highlight to see answer: C

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One Response to “Three Types of Pencils”

victoria says:

February 28, 2010 at 3:46 pm

j+k+l=32
.05j+.10k+.25l=3.40
k=2l
j+2l+l=32
j+3l=32

.05j+.10k+.25l=3.40
.05j+.10(2l)+.25l=3.40
.05j+.20l+.25l=3.40
.05j+.45l=3.40

j+3l=32
.05j+.45l=3.40
Solve for the simultaneous equations
.45j+1.35l=14.40
.15j+1.3l=10.20
.30j=4.20
j=4.20/.30=14