If you toss two coins 120 times, predict the number of times the coins will both be tails.

Question

If you toss two coins 120 times, predict the number of times the coins will both be tails.
25
30
60
90

Answer 1

Start with the basics. Every flipping of the pair can produce only four results:

 

HH

HT

TH

TT

 

Note that a quarter of the flips should result in two tails. In the short run, we shouldn't be surprised if we get several heads in a row (or tails, same idea), but over the long haul, our outcome should gradually tiptoe toward the theoretical result of:

1/4 flips are both tails.

(1/4) * 120 = 30.