Question

Andy claims that his bird can do single-digit multiplication. He shows the bird 12 cards with simple multiplication problems that are either correct or incorrect. The bird correctly identifies the correctness of the card 9 times out of 12. If the bird were simply guessing, how many would the bird be expected to get correct? (1 point)

3
9
6
12

Answer 1

If the bird were just guessing there would be two options (right or wrong) and we would expect them to be equally likely to occur (50% chance for each). A 50% of correct, out of 12 cards gives us:

12×0.50=6

If the bird was guessing we would expect 6 correct answers. (1/2 of the total correct and 1/2 wrong.)

So the answer would be 6.