The number of white balls and red balls in a jar is in the ratio of $3: 2$.

If there are 9 white balls, how many red balls are there?
(A) 5
(B) 8
(C) 2
(D) 6
(E) 3
For every 3 white balls in the jar, there are 2 red balls in the jar.

Since there are 9 white balls in the jar, which is 3 groups of 3 white balls, there must be 3 groups of 2 red balls in the jar.

Thus, there are $3 \times 2=6$ red balls in the jar.

ANSWER: (D)