What is the probability?

Question

A bag contains 10 blue marbles and 7 red marbles. A marble is drawn from the bag and not put back before a second marble is drawn. What is the probability that the first marble is blue and the second marble is red

Answer 1

B=10

R=7

P(B1) = 10/17

P(R2) = 7/16

P(1st B, then red 2nd) = (10/17)(7/16) = 70/(17)(16) = 70/272 = about 26% chance of drawing a blue first and then a red second.

10/17 is just 10 blue/total marbles = 10/(10+7) = 10/17

on 2nd draw it's total red over total marbles left = 7/16

Just multiply 10/17 times 7/16 to get 35/136 = 0.257352941 = about 26%