gmat prep question

[yvonne12]

A certain office supply store stocks 2 sizes of self stick notepads, each in 4 colors: blue, green, yellow and pink. the store packs the notepads in packages that contain either 3 notepads of the same size and the same color or 3 notepads of the same size and of 3 different colors. I fthe order, in which the colors are packed is not consumed, how many different packages of the types described above are possible?

[jayhawk2001]

A certain office supply store stocks 2 sizes of self stick notepads, each in 4 colors: blue, green, yellow and pink. the store packs the notepads in packages that contain either 3 notepads of the same size and the same color or 3 notepads of the same size and of 3 different colors. I fthe order, in which the colors are packed is not consumed, how many different packages of the types described above are possible?

We have to compute the numbers over 2 cases --

1 - Same size, same color

2C1 * 4C1 = 8

2 - Same size, 3 unique colors

2C1 * 4C3 = 8

Hence total = 16

[Cybermusings]

Whats the OA?

[yvonne12]

yes 16 is the answer,

jayhawk, can you tell me where I can go to extend my knowledge on combinatrics, its seems to be a weakness of mine.

[jayhawk2001]

yes 16 is the answer,

jayhawk, can you tell me where I can go to extend my knowledge on combinatrics, its seems to be a weakness of mine.

I found quite a bit of resources on Beat the GMAT Math wiki that
was exclusively probability and combination. That might be a good
start. After that, practice practice practice and you'll see some common
themes.

I wish I could suggest a book but unfortunately I haven't seen one
that deals exclusively with GMAT type probability questions.