- Define and explain Negative Numbers in your own words
- Use key terms such as BIDMAS accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on Negative Numbers: add, subtract and order integers below zero.
Add, subtract and order integers below zero.
Key ideas
BIDMAS
Without an agreed order, 2 + 3 × 4 could be 20 or 14. BIDMAS — brackets, indices, division and multiplication, addition and subtraction — fixes it as 14.
Place value
Each digit's value depends on its position: in 5,042 the 5 is worth five thousand and the 4 is worth forty. Zeros hold the other digits in place.
Key term — BIDMAS: The agreed order for calculations: Brackets, Indices, Division and Multiplication, Addition and Subtraction.
A shopper buys 3 packs of pens at £2.40 each and a notebook for £5. There is a 10% discount on the total. How much is paid?
Multiply first: 3 × £2.40 = £7.20. Add the notebook: £7.20 + £5 = £12.20. Find the discount: 10% of £12.20 = £1.22. Subtract: £12.20 − £1.22 = £10.98.
Answer: £10.98.
- Adding before multiplying In 2 + 3 × 4 the answer is 14, not 20 — multiplication comes before addition in BIDMAS.
- Reading 3.45 as bigger than 3.5 Compare the tenths first: 3.5 is 3.50, which beats 3.45.
Practice
14 — 3 × 4 = 12, then 2 + 12 = 14.
0.375 — 3 ÷ 8 = 0.375.
20 — 80 ÷ 4 = 20.
2 — −4 + 9 = 5, then 5 − 3 = 2.
Quick check
Which of these best defines "BIDMAS"?
Round 7.846 to 2 decimal places.
List the factors of 24.
- Negative Numbers: add, subtract and order integers below zero.
- BIDMAS: Without an agreed order, 2 + 3 × 4 could be 20 or 14.
- Prime number: A whole number greater than 1 with exactly two factors: 1 and itself, such as 7 or 13.
- Watch out for: adding before multiplying