Forty pin pong balls are in a box labeled A:10 are red ,16 are blue,and 14 are yellow.?

Question

in addition to box A ,there is a second box labeled B,which contains 10 blocks that have been numbered 1 through 10.
WHAT IS THE PROBABILITY OF DRAWING 2 RED PING-PONG BALLS OUT OF BOX A,IF AFTER THE FIRST ONE IS DRAWN IT IS PUT BACK BEFORE THE SECOND IS DRAWN?

Answer 1

You have a 10 out of 40 chance to pick a red ping pong ball (or 1 out of 4) on the first try. On your second try, because you put the ping pong ball back, you still have a 10 out of 40 chance (again, or 1 out of 4) to pick a red ping pong ball. Therefore, the probability of picking 2 red ping pong balls in a row is:

1/4 * 1/4 = 1/16

Answer 2

1/4x1/4=1/16

Theres 1 chance in 16 that a red ball will be pulled twice.