Question 1178477
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Hi
The teacher has 10 batteries, 3 of which are dead.
10 Batteries: 7G and 3B
The teacher randomly selects two batteries.

Create a probability model:
P(x=0) + P(x=1) + P(x=2) = 1

What is the expected number of good batteries the teacher selects?
 0(3C2)(7C0)/(10C2) + 1(7C1)(3C1)/(10C2) + 2(7C2)(3C0)/(10C2) 
  21/45 + 42/45 = 63/45 = 1.4

Wish You the Best in your Studies.
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