Using the number line
🎯 In this topic you will
- Use addition and subtraction to solve word problems.
- Estimate solutions using number knowledge.
- Work out doubles up to double 10.
🧠 Key Words
- double
- word problem
Show Definitions
- double: To multiply a number by two or add the same number to itself.
- word problem: A maths question written in words that describes a real-life situation to be solved.
🧮 Solving Problems with Number Sentences
When you use addition and subtraction, it is usually to solve a problem you have. Problems are often written in words, and you can write a number sentence to help solve word problems.
❓ EXERCISES
1. Solve these calculations.
a. $8 + 0 =$
b. $0 + 3 =$
c. $14 + 0 =$
d. $8 - 0 =$
e. $3 - 0 =$
f. $14 - 0 =$
👀 Show answer
b. $3$
c. $14$
d. $8$
e. $3$
f. $14$
2. Your target is $15$. Record your own way to get from $0$ to $15$. Write your number sentences.
👀 Show answer
3. Start at $11$. Your target is $0$. Record your own way to get from $11$ to $0$.
👀 Show answer
4. Write the number sentence for each word problem. Estimate the answer. Then solve your number sentence.
There were $3$ biscuits in the tin. Mum emptied a packet of $10$ biscuits into the tin. How many biscuits are in the tin now?
There were $14$ socks on the washing line. $5$ socks blew away. How many socks are left on the washing line?
👀 Show answer
$14 - 5 = 9$ socks.
5. Complete the doubles table. What will you use to help you?
👀 Show answer
🧠 Think like a Mathematician
Investigation: Aliya says all doubles are even numbers. Is Aliya correct? Explain why.
👀 show answer
- Answer: Yes, Aliya is correct. A double means adding a number to itself, which is the same as multiplying by $2$. Any number multiplied by $2$ is even, so all doubles are even numbers.