Idea 18of 23Builds onBuild a number more than one way
The little 1 is a ten moved up
What does the small 1 above a column mean when you add?
Today you'll discover
- where to start adding
- what to do with 10 or more
- why the little 1 is a real ten
Think first38 476 + 25 859, lined up by place
6 ones + 9 ones = 15 ones. What goes in the ones place?
Decide first, then press Next. Watch where each ten goes.
38 476 above 25 859 in columns under the place names, with a line for the answer. The ones column is outlined: 6 + 9 = 15, a 5 is written and a small 1 appears over the tens. Then every column is added, each sending a 1 left, and the answer reads 64 335, with the check 64 335 − 25 859 = 38 476. The last step asks for 27 685 + 46 538.
See the whole ideathe big idea and the key word, in one place
The big idea
Add place by place from the right; ten in a column becomes a 1 in the next place.
Easy to get wrongLine the numbers up by place before you start, so ones add to ones and thousands add to thousands.
Key word
- standard algorithm
- the written method that adds or subtracts column by column, starting at the right
Ready to use it?
- Add two five-digit numbers with the standard algorithm.