Arithmetic, made simple.
Arithmetic helps us count, combine, compare and share quantities. Addition, subtraction, multiplication and division are four different ways to work with numbers. Before calculating, read the question carefully and decide what the numbers represent. A correct answer should make sense in its context as well as on the page.
Add or subtract
Addition combines quantities: 18 + 7 = 25. Subtraction finds what remains or the difference between quantities: 25 − 7 = 18. For example, if you have 25 pencils and give away 7, you have 18 left.
Multiply or divide
Multiplication counts equal groups: 4 × 6 = 24 means four groups of six. Division shares a total equally or asks how many equal groups fit: 24 ÷ 6 = 4. Division by zero is undefined.
Follow the order
BODMAS means brackets, orders such as powers, division and multiplication, then addition and subtraction. Division and multiplication have equal priority, so work from left to right. Addition and subtraction also have equal priority and go from left to right.
Check with an estimate
Rounding can show whether an answer is reasonable. Five notebooks costing ₹19 each should cost a little less than ₹100, because 5 × 20 = 100. The exact cost is ₹95.
Work out 18 − 6 ÷ 3 × 2.
- Do division and multiplication before subtraction.
- Work from left to right: 6 ÷ 3 = 2, then 2 × 2 = 4.
- Now subtract: 18 − 4 = 14.
14
Take it with you: Choose the operation, follow its priority, then check whether your answer is sensible.