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If The Shoe Fits, Who Needs a Formula

In 1979, the mathematics education journal VECTOR published an article with this formula...

A Formula for Determining Shoe Size

Men: N = 3L - 25

Women: N = 3L - 22

Where L = Your foot length in inches

Task 1: Graph both of these equations on a common graph. Do they make sense? Explain.

Task 2: Devise an experiment to collect data to test the validity of these equations. Also, is it necessary to incorporate age as a factor?

Task 3: Using the Internet, search for both formulae and conversion charts for turning foot length into shoe size. Do they agree with the previous formula?

Note: This formula was published in 1979. Do you think things regarding this formula have changed in the past 35 years?


As a side note, someone once posed the following to predict someone's age from their shoe size...
  1. Ask the person to multiply their shoe size by 5
  2. Add 50
  3. Multiply by 20
  4. Add 1014 (Last 2 digits must be the last two digits of the current year)
  5. Subtract the year you were born
  6. Ask for the person's current result. The first 2 digits are their shoe size and the last 2 digits are their age. Right?