Understanding Addition with Tens and Ones
Addition combines numbers together to make a larger number. We can add a one-digit number to a two-digit number by using place value and counting forward.
- 46 + 3: Start at 46, then count forward 3 steps (47, 48, 49). The answer is 49.
- 72 + 5: Start at 72, then count forward 5 steps (73, 74, 75, 76, 77). The answer is 77.
- 58 + 2: Start at 58, then count forward 2 steps (59, 60). The answer is 60.
Always begin with the larger number and count forward. This makes addition quicker and easier.
Using Base-Ten Blocks to Add
We can use base-ten models to show addition. A “flat” stands for 100, a “stick” or “long” stands for 10, and a “cube” stands for 1. Adding means combining these models together.
- 34 + 5: 3 tens (30) and 4 ones (4). Add 5 more ones to make 9 ones. The sum is 39.
- 81 + 7: 8 tens (80) and 1 one (1). Add 7 more ones to make 8 ones. The sum is 88.
- 25 + 4: 2 tens (20) and 5 ones (5). Add 4 more ones to make 9 ones. The sum is 29.
Count the tens first, then add the ones. Using base-ten blocks helps us see the numbers clearly.
Counting Forward Strategy
When adding, we can count forward from the larger number instead of starting at one. This saves time and helps us solve problems faster.
- 63 + 6: Start at 63 and count forward 6 steps (64, 65, 66, 67, 68, 69). The answer is 69.
- 47 + 8: Start at 47 and count forward 8 steps (48, 49, 50, 51, 52, 53, 54, 55). The answer is 55.
- 90 + 5: Start at 90 and count forward 5 steps (91, 92, 93, 94, 95). The answer is 95.
Touch each number as you count forward to keep track. Counting forward is faster than starting from 1.
Solving Word Problems
We can use addition to solve real-life problems. Read the problem carefully, think about what is being added, and then use counting forward or base-ten models to find the answer.
- Emma has 52 apples. She picks 6 more. How many apples does she have now? 52 + 6 = 58
- A box holds 67 crayons. Add 2 more crayons. How many crayons are there? 67 + 2 = 69
- Jack has 43 marbles. His friend gives him 7 more. How many marbles does Jack have? 43 + 7 = 50
Underline the numbers in the problem and decide what to add. Always check your answer by counting forward again.