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

Homework Help: Discrete math's-Counting

  1. Dec 2, 2008 #1
    1. The problem statement, all variables and given/known data

    use combinatorial methods to determine the smallest amount of money that using cents, nickels, dimes, or quarters, requires
    a) four coins
    b) five coins
    c) six coins
    d) seven coins
    e) eight coins

    Hint: Consider the ways to partition sets of those respective sizes and calculate their minimum values.

    2. Relevant equations

    3. The attempt at a solution

    a) four coins => 4 cents (1cent+1cent+1cent+1cent)

    b) five coins => 9 cents (1nickel + 4 cents)

    c) six coins => 19 cents (1 nickel + 1 dime + 4 cents)

    I don't know how to do d) ans e)

    I can't use 5 cents , because this is makes 1 nickel.

    Please help. Thank you.
  2. jcsd
  3. Dec 2, 2008 #2
    By similar reasoning:
    You can't use 2 nickels because they make 1 dime.
    You can't use 2 dimes and 1 nickel because they make 1 quarter.
    These restrictions help you pick the next coin, but the question requires the use of combinatorial methods.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook