Question

Ryan has a pack of 10 pens. 3 pens are red, 4 are black, and 3 are blue. What are the chances that he pulls out a red pen ar black pen? Assume that the pens are pulled without replacement. Round to the nearest whole number.

Answer 1

The phrase is ambiguous. Two common interpretations:

1) If he draws just one pen: the chance it is red or black = (3+4)/10 = 7/10 = 70%.

2) If he draws two pens without replacement and you want the chance he gets one red and one black (in any order):
P = P(R then B) + P(B then R)
= (3/10)(4/9) + (4/10)(3/9) = 24/90 = 4/15 ≈ 26.67% ≈ 27% (nearest whole number).

If you meant something else, tell me how many pens are drawn.