- Define and explain Adding Two Numbers in your own words
- Use key terms such as Sum accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
Adding joins things together and subtracting takes them away. These two ideas are the engine of almost all early mathematics.
This lesson focuses on Adding Two Numbers: combine two groups and count them all to find the total.
Combine two groups and count them all to find the total.
Key ideas
Counting all
Put two groups together and count everything from the start to find the total. This works well with small numbers and real objects like beads or blocks.
Counting on and back
Start from the first number and count on for addition, or count back for subtraction. This is much quicker than counting everything from 1 each time.
Key term — Sum: The answer when you add numbers together. The sum of 4 and 6 is 10.
7 + 5 = ?
12 — start at 7, then count on: 8, 9, 10, 11, 12.
Answer: 12 — start at 7, then count on: 8, 9, 10, 11, 12.
- Forgetting to count on from the bigger number Start at the larger number and count on the smaller jump to save steps and avoid slips.
- Writing 3 + 4 as 34 The + sign means join the amounts into one total of 7, not write the digits side by side.
Practice
9 — count back: 14, 13, 12, 11, 10, 9.
6 — 4 + 6 = 10.
14 — 9 + 5 = 14.
12 — 20 − 2 = 18, then 18 − 6 = 12.
Quick check
Which of these best defines "Sum"?
Write the fact family for 6, 9 and 15.
- Adding Two Numbers: combine two groups and count them all to find the total.
- Counting all: Put two groups together and count everything from the start to find the total.
- Difference: The answer when you subtract.
- Watch out for: forgetting to count on from the bigger number