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Monday, May 20, 2013

# The King’s Chessboard: The Power of Doubling

### Skills Covered: reading, addition/multiplication, calculator skills, problem solving, charting data

The King’s Chessboard by David Birch is a fantastic book – both for math and character training.  In it, the king foolishly agrees to doubling a gift of rice everyday for the number of days on a chessboard.  Because he doesn’t know about the power of doubling, he loses A LOT of rice.

Reading the book is a great way to start off a lesson on the power of doubling.

After reading, ask your child, “What if I offer to pay you 2¢/day for doing the dishes every night for 20 days?  How much money would you make?

(Hint: 2¢ x 20 days = 40¢.  Yes, ONLY 40¢!)

Now ask, “What if I offer to pay you 2¢ the first day and double that each day for 10 days?  Would it be worth it to you?”

(Hint: Make a chart like the one pictured above and allow your child to use a calculator to double the amount each day.  Remember – on the 10th day, add each day’s wages together to get the total earned over 10 days.)

“Hmmm…You think \$20+ is fairly worth your effort for 10 days, huh?  Well, what if I continue doubling your money until 20 days are up?  Would you care to dishes nightly then?”

(Hint: Keep doubling on the chart through 20 days.  Again, add all the days wages together to get the total earned over 20 days.)

“Yes?  Yes?  You’d like to make that deal?  Let me know when you find someone willing.  We’ll both go to work for him!”

### A Similar Lesson

You might be interested:  We did a similar lesson a few years ago using another fabulous book, One Grain of Rice.

Need a living math “how-to” guide? You might like Loving Living Math!

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