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## Homework Statement

In how many ways can 12 balls be arranged into 4 different rows with each row having

at least one ball

(a) if the balls are identical?

(b) if there are 6 identical red balls and 6 identical blue balls?

## Homework Equations

## The Attempt at a Solution

a)

Put 4 balls in each row.

Remaining 8 balls left.

Label each row A, B, C, D

A + B + C + D = 8 balls

Ans: 11C3 = 165 (Correct)

b) (Unsure how to do)