Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Simple coin tossing question, confused on their answer

  1. Nov 10, 2006 #1
    Hello everyone. I"m just wondering why they solved the answer in this manner.

    The question is:
    A coin is tossed 4 times. Each time the result H for heads or T for tails is recorded. An outcome of HHTT means that heads were obtained on the first 2 tosses and tails on the second 2. Assume heads and tails are equally like on each toss.

    Well they solved it this way:
    There are 4 outcomes in which exactly one head can occur (since a string of one "T" and three "H"'s can have
    the "T" in any one of the string's four positions). So the probability of exactly one head is 4/2^4 = 1/4.

    Okay I understand that there are 2^4 possible outcomes on 4 tosses, 2 chocies can happen, either a H or a T, so 2^4.

    But Why did they say, since a string of one "T" and 3 "H"'s. If we are trying to find how many times you get exactly 1 head Why wouldn't they say the following:
    since a string of one "H" and three "T"s can have the "H" in any one of the strings for positions, such as HTTT, THTT, TTHT, TTTH, this shows its 4 ways, in which you will get exactly 1 head. I'm just confused on why they worded it that way or am I missing somthing?

  2. jcsd
  3. Nov 10, 2006 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    It's probably just an error in the book.
  4. Nov 10, 2006 #3
    I thought so, but just wanted to make sure, the professor actually did the solution but either way it would come out to the same answer just making sure. thanks!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook