Ok, so I'm a parent helping my 12yo with a 7th grade math question. We couldn't figure out the right way to get the answer for this one...
Q: A coin is flipped 3 times. What is the probability of getting at least 2 tails?
I thought the answer would be 1/2 x 1/2 which would equal 1/4 with the third flip not mattering, but that's not correct. Listing the outcomes (H being heads and T being tails... HHH, HHT, HTH, HTT, THH, THT, TTH, TTT), it's clear that 1/2 the outcomes result in at least 2 tails. So, is there a way to figure this out mathematically as a function of fractions, with each coin toss being a 1/2 probability? Is listing the outcomes and counting from there the only way?
Thanks in advance!