Doubles Plus One
Doubles plus one (also called near doubles) is a strategy for adding two numbers that are just 1 apart, like 3 + 4 or 5 + 6. Instead of counting, you use a doubles fact you already know and add 1 more.
If you know 3 + 3 = 6, then 3 + 4 = 6 + 1 = 7. This is a quick trick for mental maths!
What is Doubles Plus One - Class 1 Maths (Addition (Grade 1))?
A double is when you add a number to itself: 2 + 2, 3 + 3, 4 + 4, etc.
Doubles plus one means: when two numbers are just 1 apart, use the double of the smaller number and add 1.
a + (a + 1) = double a + 1
Doubles facts to remember:
| Double | Answer |
|---|---|
| 1 + 1 | 2 |
| 2 + 2 | 4 |
| 3 + 3 | 6 |
| 4 + 4 | 8 |
| 5 + 5 | 10 |
| 6 + 6 | 12 |
| 7 + 7 | 14 |
| 8 + 8 | 16 |
| 9 + 9 | 18 |
Solved Examples
Example 1: Example 1: Basic Doubles Plus One
Question: Find 3 + 4 using doubles plus one.
Think:
- 3 and 4 are 1 apart
- Double of 3 = 3 + 3 = 6
- Add 1 more: 6 + 1 = 7
Answer: 3 + 4 = 7.
Example 2: Example 2: Another Near Double
Question: Find 5 + 6.
Think:
- Double of 5 = 10
- 10 + 1 = 11
Answer: 5 + 6 = 11.
Example 3: Example 3: Order Does Not Matter
Question: Find 8 + 7.
Think:
- 7 and 8 are 1 apart
- Double of 7 = 14
- 14 + 1 = 15
Answer: 8 + 7 = 15.
Example 4: Example 4: Small Numbers
Question: Find 1 + 2.
Think:
- Double of 1 = 2
- 2 + 1 = 3
Answer: 1 + 2 = 3.
Example 5: Example 5: Word Problem
Question: Ria has 4 red bangles and 5 blue bangles. How many bangles in all?
Think:
- 4 + 5 = double 4 + 1 = 8 + 1 = 9
Answer: Ria has 9 bangles.
Example 6: Example 6: Is It a Near Double?
Question: Can I use doubles plus one for 4 + 7?
Think:
- 7 − 4 = 3 (they are 3 apart, not 1)
Answer: No, 4 + 7 is not a near double. Use this strategy only when numbers are 1 apart.
Example 7: Example 7: Missing Number
Question: 6 + ___ = 13. Is this a doubles plus one problem?
Think:
- Double of 6 = 12, double plus 1 = 13
- So 6 + 7 = 13
Answer: The missing number is 7. Yes, it is a doubles plus one problem.
Key Points to Remember
- Doubles = adding a number to itself (4 + 4 = 8).
- Doubles plus one = when two numbers are 1 apart, double the smaller and add 1.
- This strategy works for: 1+2, 2+3, 3+4, 4+5, 5+6, 6+7, 7+8, 8+9.
- Memorise doubles facts (1+1=2 up to 9+9=18) for fast mental maths.
- Doubles plus one only works when numbers differ by exactly 1.
Practice Problems
- Find 2 + 3 using doubles plus one.
- Find 6 + 7 using doubles plus one.
- What is double 4? What is double 4 plus one?
- Aman has 7 red marbles and 8 blue marbles. Use doubles plus one to find the total.
- Can you use doubles plus one for 3 + 5? Why or why not?
- Fill in: 9 + 10 = double ___ + 1 = ___.
Frequently Asked Questions
Q1. What is doubles plus one?
Doubles plus one is a strategy for adding two numbers that are 1 apart. You double the smaller number and add 1. For example, 4 + 5 = (4+4) + 1 = 9.
Q2. When can I use this strategy?
Use it when the two numbers you are adding are exactly 1 apart, like 3+4, 5+6, or 8+9.
Q3. What doubles facts should I know?
Memorise: 1+1=2, 2+2=4, 3+3=6, 4+4=8, 5+5=10, 6+6=12, 7+7=14, 8+8=16, 9+9=18.
Q4. Does the order matter?
No. 5+6 gives the same answer as 6+5. You can double the smaller number in either case and add 1.
Q5. What if the numbers are 2 apart?
Then it is called 'doubles plus 2.' For example, 4+6 = double 4 + 2 = 10. But in Class 1, we mainly practise doubles plus 1.
Q6. Why is this strategy useful?
It makes addition faster. Instead of counting up one by one, you use a doubles fact you already know and quickly add 1 more.
