Question

In a mall, three neighboring stores offer discount coupons. Store A has 300

envelopes, Store B has 600 envelopes, and Store C has 900 envelopes. Each envelope

contains one, two, or three coupons. The following table shows the number of

envelopes according to the number of coupons in them in each store.

Store\#Coupons	1	2	3	Total
A	200	100	0	300
B	300	200	100	600
C	400	300	200	900

Each customer selects an envelope from each store and gets coupons in it. Rebecca

went to the mall when it opened, and became the first customer for all three stores.

She randomly selected an envelope from each store. After visiting the three stores,

Rebecca found that she received 4 coupons. What is the probability that she received

two coupons from Store A?

Answer 1

Heve we want to find P(+oo ccupo n s m, m Store given thost she received 100 Coupons 台PL2 coupons -from store A and Couupons from Sore B and )couponsrom store P ( coupons) 1800 800 900 -Do 300 -х 400. 1800 8co 18 1 300 大320-K 1801800 1800 P(IA, 19, 1) 200 十( 260-k 200 k 400 800 300 2 o0 800 800 800 206300 1800 806 1800 8oo PC OA, 30, ) PLDA, 28, 2c) 12000000 18o0o006oooo+600004 1goo 十(40000ナ1800)+ ( 60000 *1800 1 200000o l 2. -334 oooooo 334