GMAT PREP combination pblm

[warlock]

can anyone explain me the solution..

thank you

OA:C

[rishi235]

Hi this is how i worked on it

A) 3 notepads of the same size & same color
Lets consider a stick of 1st size
The figure 3 is just to add to the confusion
1 size notepad => 4 colors...Hence 4 different types=> 4 packages (for 1 type of notepad)

B) 3 notepads of the same size & different colors
Consider only 1 type of notepad
Here we need the number "3"...
v need 3 different colors....we have total 4 colors...
=> 4C3 = 4 packages (for 1 type of notepad)

Hence for the 2 types of notepads
2(4+4) = 16...

If theres a better method...pls share

[ramyaravindran]

Let's assume that the 2 different sizes are Size 1 and Size 2. Size 1 and Size 2 are both available in Blue, Green, Yellow and Pink. (i.e)

1Blue,1Green,1Yellow,1Pink,2Blue,2Green,2Yellow and 2Pink.

We are given that the above are packaged such that there are 3 notepads of same size and color or there are 3 notepads of same size and 3 different colors.

3 notepads of Same Size and color can be package in 8 ways (Say 3 notepads of Size 1 blue, 3 notepads of Size 1 Green ...etc)

3 notepads of same size and 3 different colors can be packaged in 4C3 ways for Size 1([1Blue,1Green,1Yellow],[1Blue,1Yellow,1Pink],[1Green,1Yellow,1Pink],[1Blue,1Green,1Pink])

Similarly it is 4C3 ways for Size 2.

This comes to a total of 8+4C3+4C3 ways = 16