Bedtime Math adds a little calculation to the nighttime routine


The Web site Bedtime Math. (Screen shot/Screen shot)

When Laura Overdeck’s oldest child was 2, she and her husband added a math problem to their nightly bedtime-story routine. Overdeck and her husband, John, both grew up in houses where math was treated as something playful and fun, and they wanted to pass that on to their children.

It started with tallying the number of eyes or noses on the stuffed animals in her bed. As their daughter got older, they worked in addition and subtraction. Some years later, the girl’s little brother began demanding his own bedtime math problem: For Overdeck’s children, math had become as much of a treat as dessert.

She started publishing the problems in an e-newsletter, then launched an app and a Web site. Her first book, “Bedtime Math: A Fun Excuse to Stay Up Late,” was published in June, 2013. Another one, titled “Bedtime Math 2: This Time It’s Personal,” is coming out March 11.

“We stumbled on something that’s a pretty simple idea, but somehow it’s revolutionary,” Overdeck said, adding that she wants to see people embrace math the same way they do reading.

Each problem on the site has a short introduction followed by questions for four age groups or ability levels. Here is an example Overdeck shared with The Post:

Igloos gone wild

Igloos are small homes built by stacking blocks of ice or packed snow in a spiral that goes around on top of itself, not in rows that start and end at the same height. Usually it’s plain white ice or snow cut from nature, but one couple decided to make their own multicolored igloo. They saved up box-shaped milk cartons, filled them with water and a few drops of food coloring, then let them all freeze into beautiful colored ice blocks.

Wee ones: If the couple used blue, red, green, orange and yellow blocks, how many colors does the igloo have?

Little kids: If the main body of the igloo uses 100 blocks and the entrance uses 40, how many blocks were used? Bonus: If 10 of those blocks are pink, how many blocks are other colors?

Big kids: If the igloo builders saved 50 cartons of milk, and each carton holds eight cups, how many cups of milk did they have to drink to make this igloo? Bonus: If it took 5½ hours for the water to freeze through and the first carton was filled at 10:30 a.m., at what time was the first block ready for building?

The sky’s the limit: If the igloo has (roughly speaking) 10 layers, and each layer has four more blocks than the one above it, and it uses 600 blocks total, how many blocks are there in the bottom, biggest layer?

Answers

Wee ones: Five colors!

Little kids: 140 blocks. Bonus: 130 non-pink blocks.

Big kids: 400 cups of milk. Bonus: At 4 pm.

The sky’s the limit: 78 blocks. If there are b blocks in the bottom layer, then the 10 layers have b+(b-4)+(b-8)+. . .up to (b-36) blocks. This is the same as 10b–4x(1+2+3…+9), or 10b–(4x45) (if you know the triangle shortcut formula: for a triangle with the biggest number t, the total is t x (t+1)/2).

So we now have:

10b–180=600

10b=780

b=78=the number of blocks in the bottom row.

Mari-Jane Williams covers parenting and family issues for Local Living and schools for the Prince William and Loudoun Extras.
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