dangerous compassions

I call you / from the comet's cradle

Tuesday, November 14, 2006

math problem

This morning there was a beautiful large starling on a branch outside the bedroom window where lots of birds like to perch, and a squirrel likes to sit too. It made cute sounds and flapped its wings in that helpless-looking way--it looks almost like shrugging--before flying off quickly.

If you flipped three pennies, what are the odds that they all came out the same?

1 in 3
1 in 4
1 in 8

I know I have heard answers to this type of question many times, but I never know who to trust. My ex-best friend Melly, who majored in math, would know. Where's Mel when I need her.


  • At November 16, 2006 1:59 PM, Anonymous Anonymous said…

    This is Kat, who just took a statistics class last semester.

    When you flip three coins, they can come out the following ways:
    HHH,HHT,HTH,THH,TTH,THT,HTT,TTT. That's eight ways, two of which have all the coins being the same. So the chances of the coins being the same are two in eight, which is also one in four.

    I love math.

  • At November 16, 2006 2:11 PM, Blogger robotmadder said…

    Thanks, Kat! That's what Erik told me too. I like the way you explain it with the visual aid. Maybe you would make a good teacher.

    Yes, I think the 1/4 choice is there to throw people off who would forget TTT and HHH both would be acceptable.


  • At March 12, 2010 11:02 AM, Blogger James said…

    There's an even easier way to think of it. Flip one coin, it doesn't matter whether it's heads or tails, you just need to match it twice.

    So you have a 50/50 (or half) chance on the second, and a 50/50 (again, half) chance on the second.

    A half times a half is a quarter! Hey presto, 1/4!

  • At September 24, 2015 10:24 AM, Blogger Cassandra ervin said…

    That's probability though, not odds. The odds are the same whether you flip on or 100 coins so it would be 50/50 for all three coins which would leave you with 1.3 ODDS.


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