Math Brain Teaser: How to Choose a Mans Shirt

You have been invit­ed to an impor­tant fundrais­ing gala at your old col­lege and decid­ed that this black-tie event demands a short col­lar super white Ital­ian shirt, like the one you bought years ago for your wed­ding. When you brave­ly tried the wed­ding shirt on (size 16), your wife not­ed that the col­lar suf­fo­cates you and you need about 1/4″ more space every­where in-between your neck and the col­lar all around your neck. What size shirt do you need to buy?  In case you don’t know the shirt size 16 means that a tape wrapped around your neck and two fin­gers posi­tioned flat upfront will mea­sure 16 inches.

(Puz­zle answer is below. Please try to solve it before check­ing out the answer!)

Maria Lan­do (aka The­Math­Mom) illu­mi­nates and demys­ti­fies math­e­mat­ics for adults, describ­ing its fun use in every­day life. The­Math­Mom has been fea­tured in the Boston Globe, The Jew­ish Advo­cate, and Red­book Mag­a­zine. Her week­ly newslet­ter con­tains sto­ries and puz­zles for the whole fam­ily, and tips on per­ceiv­ing math and pre­sent­ing it to kids as a toy, a tool, and a friend. Learn more at www.TheMathMom.com.

Puz­zle answer
Yes, sur­pris­ing use of math in the dress­ing room to refresh our geom­e­try. Shirt col­lar is almost cir­cu­lar, and cir­cle cir­cum­fer­ence = 2 x Pi x Radius. The shirt size 16 means that a tape wrapped around your neck and two fin­gers posi­tioned flat upfront will mea­sure 16 inches.

At the time of your wed­ding: 2 x Pi x Radius of your neck = 16.
Now: 2 x Pi x new Radius of your neck = 2 x Pi x (wed­ding Radius of your neck + 1/4) = 2 x Pi x wed­ding Radius of your neck + 2 x Pi x 1/4 = 16 + Pi/2 = 16 + 3.14/2 = 17.57 (approx). So, you are more around size 17.5 now.

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