intro: Fans of math and pie are celebrating "Pi Day" or March 14, representing the ratio of a circle's circumference to its diameter, or approximately 3.14159.
National Pi Day became a national holiday after the House of Representatives designated it as such in 2009 with a resolution that "encourages schools and educators to observe the day with appropriate activities that teach students about pi and engage them about the study of mathematics."
Here are some ways to celebrate Pi Day, pies, and Friday:
quicklist: title: Momofuku Milk Bar category: media: 22912289 text: Momofuku Milk Bar stores in New York City today are featuring a special "Pi Day" Crack Pie dusted with the Pi symbol. The 10" whole pies, $44, have "toasted oat crust" and "gooey butter filling," Milk Bar says. As always, you can get just a slice for $5.25 at all stores, or order a traditional whole Crack pie online at milkbarstore.com.
Milk Bar opened in 2008 as the dessert branch of chef David Chang’s Momofuku restaurant group, headed by the nominee for the upcoming 2014 James Beard Outstanding Pastry Chef award, founder and owner Christina Tosi.
quicklist: title: Magnolia Bakery category: media: 22912356 text: Magnolia Bakery is offering caramel apple hand pies today for $3.00 each. The New York City-based bakery is also selling a selection of mini icebox pies for $8 in a range of flavors, including banana cream, blueberry jamboree, Snickers, peanut butter, and chocolate pudding.
quicklist: title: Bakers Square category: media: text: Bakers Square is offering all educators $2 off whole pies today in celebration of Pi Day. The restaurant chain has locations in six states: Iowa, Illinois, Indiana, Minnesota, Ohio and Wisconsin.
quicklist: title: Pizza Hut category: text: In celebration of Pi Day, for three hours, between 1 and 4 p.m. CST (i.e. 3.14), Pizza Hut will give away 140 gift cards ($10 each) when people use the hashtag #PizzaHutPiDay on Twitter.
quicklist: title: Sbarro category: text:
Pizza chain Sbarro will choose 50 random winners to get a free slice of pizza if they answer this question correctly: What famous scientist shares a birthday with National Pi Day? The chain announced the details of the contest at 11 a.m. ET on Friday on its Facebook page and will announce the winners at 10 a.m. on Saturday.
The chain will also offer a regular daily special of two pies for $20 with any toppings.
quicklist: title: Whole Foods category: text: Offers will vary by regional Whole Foods Markets, a spokeswoman for Whole Foods told ABCNews.com. Many stores will host activities such as tastings, pie eating contests, pie a la mode, pie walks and warm pie sold out of the rotisserie.
Rocky Mountain: Weekend sale -- all large fruit pies will be $12.99 (regularly $14.99)
North Atlantic: All large fruit pies will be $12.99 (regularly $14.99)
Southern Pacific: Two 9-inch pies for $16
Florida: Two handheld pies for $3.14 for the weekend
South: On Friday, save $3.14 on large fruit pies -- $9.85 each
Mid Atlantic: On Friday, save $6 on apple pie ($9.99 each)
Northern California: All Made Right Here pies on sale for $14.99 (regularly $19.99)
Midwest: Eight-inch fruit pies $6.99 (regularly $8.99) and fruit pie slices $1.99 (regularly $3) on Friday
Pacific Northwest: $5 off large fruit pies ($7.99-$8.99)
quicklist: title: Starbucks category: text: Starbucks isn't offering a deal on pies, but it's hard to pass up a free grande (16 oz.) hot brewed coffee. That's what you get with the purchase of any breakfast sandwich through Friday at participating coffee shops.
quicklist: title: Petsi Pies, Massachusetts category: text: Not too far from the Massachusetts Institute of Technology, Harvard University and other venerable bastions of mathematics, Petsi Pies in the Bay State will have pie challenges starting at 1:59 p.m. Why? Pi is 3.14159, Petsipies.com says, adding:
For a free Cutie Pie we ask that you verbally recite 10 digits of pi.
For a free large pie we ask that you verbally recite 314 digits of pi.
For a free Pie per Season gift card (four pies total) we ask that you verbally recite 628 digits of pi.
quicklist: title: Jamba Juice category: text:
Again, not a pie, but a worthy Friday deal: Jamba Juice is offering $2 fruit and veggie small smoothies or 12 oz. fresh juice blends, or you can upgrade by paying for a larger size. Participating locations will accept coupons through Sunday.
quicklist: title: Einstein Bros. category: text: If salmon sandwiches were "pies of the sea,' then Einstein Bros.' buy one, get one free salmon sandwich deal would be spot on for Pi Day. Get a free Honey Smoked or Nova Lox salmon sandwich after you purchase one, with a coupon.
Do you have Pi Day and Friday freebies you want to share? Let us know in the comments.