Double-Trouble or Split-It!

Recently we have added a "game" to our EDC notebooks. Double-Trouble and Split-It are games that are designed to get students to strategically think about doubling and splitting numbers. These skills are crucial if a student is to build great mental number sense.

For example:

When I ask kids to split 1,700, many kids balk, because they see 17 groups of 100 as an odd number of hundreds. Most kids are not seeing this as 8 1/2 groups of 100. However, most students can readily replace 1,700 with 1,600 + 100, and they can easily split these numbers to get to 850! This still may not seem important, but since the product of 17 X 10 is so easily calculated, it seems logical that 17 X 5 (half as big as 17 X 10) should be easily found if 1,700 can be easily split.

In a similar way, being able to double numbers with ease leads to being able to double small factor pairs into larger factor pairs. If 7 X 2 = 14, then 7 X 4 is twice as big. So, 7 X 4 = 28. Then, 7 X 8 = 56, and 7 X 16 = 112...likewise, 17 X 2 = 34, 17 X 4 = 68...17 X 4 = 68, 17 X 40 = 680, and 17 X 80 = 1,360 ...all done through doubling.

When doubling a number, many students find it easiest to double the largest place value first and then work through the smaller place values.

Doubling a number like 1, 486 might look like 1,000 + 1,000 = 2,000...400 +400 = 800 ...80 +80 = 160...6 + 6 = 12...added together, the sum is 2,972.

These are VERY important concepts! Please practice. It's the kind of thing you can do in the car.