Brain Teaser: What shirt size you need now?

You have been invit­ed to a fundrais­ing gala and decide that this black-tie event demands an ele­gant white Ital­ian shirt — just like the one you got years ago for your wedding.

When you find and brave­ly try the wed­ding shirt (size 16) on, you and your wife notice that the col­lar suf­fo­cates you — you absolute­ly need 1/4″ more space every­where in-between your neck and the col­lar all around your neck.

So you’ll need a new shirt.

Brain teas­er: What size shirt do you need to buy?

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

PS: In case you don’t know, shirt size 16 means that a tape wrapped around your neck and two fin­gers posi­tioned flat upfront will mea­sure 16 inches. 

Maria Lan­do (aka The­Math­Mom) illu­mi­nates and demys­ti­fies math­e­mat­ics for adults, describ­ing its fun use in every­day life. The­Math­Mom has been fea­tured in mul­ti­ple media out­lets includ­ing The Boston Globe, The Jew­ish Advo­cate, and Red­book Mag­a­zine. Learn more at TheMathMom.com.

Puz­zle answer

Yes, math can come handy in the dress­ing room, so let’s refresh our geom­e­try. A shirt col­lar is almost cir­cu­lar, and as you prob­a­bly remem­ber cir­cle cir­cum­fer­ence = 2 x Pi x Radius. 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.

But 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.

Hap­py shopping!

More fun brain teaser games to challenge your cognitive skills:

• Can you read this face?
• Top 25 Brain Teasers and Puz­zles for teens and  adults of any age