Next 10
How many are needed to reach the next 10?
Script by Prof. Mahesh Sharma at Center for Teaching & Learning Mathematics
When adding, what is the next 10 to the largest number?
How many are needed reach the next 10?
Where do you get it?
What's left?
Add what's left to the next ten to combine the numbers.
EXAMPLE A: 3 + 9 = ?
Take the largest digit: 9
How many to reach 10? 9 + 1 = 10
Take 1 from 3: 3 - 1 = 2
Add the difference to 10: 10 + 2 = 12
EXAMPLE B: 7 + 8 = ?
Take the largest digit: 8
How many to reach 10? 8 + 2 = 10
Take 2 from 7: 7 - 2 = 5
Add the difference to 10: 10 + 5 = 15
EXAMPLE C: 47 + 8 = ?
Take the largest number: 47
How many to reach the next 10? 47 + 3 = 50
Take 3 from 8: 8 - 3 = 5
Add the difference to the next 10: 50 + 5 = 55
EXAMPLE D: 47 + 8 = ?
Take the largest number: 47
How many to reach the next 10? 47 + 3 = 50
Take 3 from 8: 8 - 3 = 5
Add the difference to the next 10: 50 + 5 = 55
EXAMPLE E: 246 + 7 = ?
Take the largest number: 246
How many to reach the next 10? 246 + 4 = 250
Take 4 from 7: 7 - 4 = 3
Add the difference to the next 10: 250 + 3 = 253
EXAMPLE F: 529 + 36 = ?
Take the largest number: 529
How many to reach the next 10? 529 + 1 = 530
Take 1 from 36: 36 - 1 = 35
Add the difference to the next 10: 530 + 35 = 565
EXAMPLE G: 1,574 + 98 = ?
Take the largest number: 1,574
How many to reach the next 10? 1,574 + 6 = 1,580
Take 6 from 98: 98 - 6 = 92
Add the difference to the next 10: 1,580 + 92 =
9 tens, how many to make 10 tens? 1
Take 1 from 8 tens to make 7 tens = 1,570 + 102 = 1,672
EXAMPLE H: Standard Algorithm (Procedure)
You are still making ten, recording the 10 in the next column to the left, and are noting what remains beneath the line.
For example, 10 ones are 1 ten. 10 tens [100] are 1 hundred. 10 hundreds [1000] are 1 thousand.
1,574 + 98 = ?
1,574
0 +98
1,672
COMBINE THE ONES: 4 + 8 = 12
8 + 2 + 2 = 10 + 2 = 12
10 + 2 = 12
Add 1 ten to the tens column.
COMBINE THE TENS: 1 + 7 + 9 =
(9 + 1 = 10) + 7 = 17 TENS = 170
Record the 7 in the tens place beneath the line and add the 1 to the hundreds column.
COMBINE THE HUNDREDS: 1 + 5 = 6
Record the 6 in the hundreds' place below the line.
COMBINE THE THOUSANDS: 1 + 0 = 1
Record the sum in the thousand's place beneath the line: 1
READ THE RESULT:
1,672