Raial has 7 different posters to be hanged in her bedroom, living room and kitchen. Assuming she has plans to place at least a poster in each of the 3 rooms, how many choices does she have?
A. 49 B. 170 C. 21 D. 210
Correct Answer: D
Explanation
The first poster has 7 ways to be arranges, the second poster can be arranged in 6 ways and the third poster in 5 ways. = 7 x 6 x 5 = 210 ways or \(\frac{7}{P_3}\) = \(\frac{7!}{(7 - 3)!}\) = \(\frac{7!}{4!}\) = \(\frac{7 \times 6 \times 5 \times 4!}{4!}\) = 210 ways
