A box contains four 40-W bulbs, ﬁve 60-W

bulbs, and six 75-W bulbs. If bulbs are se-

lected one by one in random order, what is

the probability that at least two bulbs must be

selected to obtain one that is rated 75W?

Question

Mike Baxter

22 November, 05:49

+4

Answers (1)

Know the Answer?

Kailey Osborn · Answer 1

So first one is not a 75W bulb:

P (not a 75Wbulb) = (4+5) / (4+5+6) = 9/15

P (a 75W bulb) = 6 / (15-1) = 6/14

9/15*6/14=9/35

A box contains four 40-W bulbs, ﬁve 60-Wbulbs, and six 75-W bulbs. If bulbs are se-lected one by one in random order, what isthe probability that at least two bulbs must beselected to obtain one that is rated 75W?