• Log In
  • Sign Up
    • One of my followers is blowing up #MTBoS Twitter with this challenge:

      I was watching TV last night and this was a great math question that came up! How would YOU solve it? Show me below!!

    • By inspection -

      Answer D is not possible 16 dimes is >1 dollar,

      Answer C is not possible 12 dimes is $1.20

      Answer A is inaccurate - 4 dimes is 40 cents and 2 nickels makes 50 cent, in total

      The only answer left is B - So, 8 dimes is 80 cents and 4 nickels is 20 cents which is one dollar

      So answer B is the correct answer by inspection and verified by adding 8 dimes and 4 nickels


    • 5th grade arithmetic approach: there are two dimes per each nickel. Make it a "group", which is 25c, and keep adding up groups until you hit $1 (or just divide 1 by .25). You get four groups, which makes 4 nickels.

      8th grade approach: a standard system of two linear equations:

      10x + 5y = 100, x = 2y => 20y + 5y = 100, x = 2y => y = 4, x = 8

      I would not be able to do this simple math in a stressful and time-limited situation of a TV show, so arithmetic method or test/exclusion as Pathfinder did works better in this case.

    • I thought briefly about the two linear equations; but I realized by the time I wrote them out and solved them - like you I need paper and a pencil to parse them out - I already had my answer by inspection.

      I always say it is good to know more than just one way to skin a cat.

    • I started with the fact that he could not have ten dimes or more, therefore any number greater than 5 had to be wrong.

      Then I calculated B and it was correct.