Here a good one
A manufacturer produce x percent more video cameras in 1994 than in 1993 and y percent more video cameras in 1995 than in 1994. If the manufacturer produced 1,000 video cameras in 1993, how many video cameras did the manufacturer produce in 1995?
1) xy = 20
2) x + y + xy/100 = 9.2
In 1995 the manufacturer produced 1000*(1 + x/100)*(1+ y/100) cameras, or 1000*(1 + x/100 + y/100 +xy/100^2).
(1) Not enough info. We need x, y, and xy. Insuff => B, C, or E.
(2) x + y + xy/100 = (x/100 + y/100 + xy/100^2)*100. With this info we could indeed solve the problem => B.