What if you could build your own house out of Lego? How many pieces would you need? Luckily for us, a company made an online calculator to help figure that out. You type in your house size in square-foot area, and the number of floors. The calculator uses math to say how many 8-peg Lego bricks are needed to build that house! How does it do it? We know that a Lego brick is about 1/4 inch thick, 5/8 inch wide, and 1 1/4 in long. Meanwhile, a real clay brick is 2 1/4 x 4 x 8 inches. So you need 359 Lego bricks for each real one. Turns out you need more than 10 million Legos to build your average 2,000-square-foot house. But watch out: that covers only the outside walls. If you want lots of inside walls to make rooms, you’ll need even more Lego!

*Wee ones:* A Lego brick is shaped like a box. How many faces (flat sides) does it have? Find a box and count them up!

*Little kids:* If you start building your bedroom wall with 2 red bricks, 2 yellow, 2 blue, 2 green and 2 white, how many bricks is that? *Bonus:* If you put 2 8-peg Lego bricks next to each other, how many pegs do you have in total – and how many ways can you place the 2 bricks so pegs line up? (Assume they’re the same color.)

*Big kids:* The square foot area of a space is the length times the width. If your bedroom is 10 feet long by 9 feet wide, how many square feet do you have? *Bonus:* If the two long walls in that 10-million brick house each have 1 million more bricks than each of the 2 short walls, how many bricks are in each wall?

*The sky’s the limit:* If your bedroom covers 20 square feet, what are all the combos of lengths and widths that it could be (using only whole numbers) — and which combo would need the most length of wall?

__Answers:__

*Wee ones:* 6 faces – remember to count the top and bottom along with the 4 side faces!

*Little kids:* 10 bricks. *Bonus:* 16 pegs. There are 5 ways to line them up: side by side in a square, end to end in a line, a T (one pointing to middle of the other), and 2 ways to make an L.

*Big kids:* 90 square feet. *Bonus:* 3 million bricks in each long wall, and 2 million in each short wall. Each long and short together use half the bricks – 5 million – and then you need 2 numbers 1 million apart that add to 5 million.

*The sky’s the limit:* 3 combos: 1 foot by 20 feet, 2 by 10, and 4 by 5. The 1 by 20 will need 42 feet of wall (20 + 20+ 1+ 1), while the 4 by 5 needs only 18 feet (5 + 5 + 4 + 4). The proportions of the space makes a huge difference!

Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.