The four operations

Use the four operations (add, subtract, multiply, divide) with integers, fractions and decimals. When a calculation has more than one operation, use the order of operations: brackets first, then powers and roots, then multiplying and dividing, then adding and subtracting.

Never work from left to right. Multiply or divide before you add or subtract.

Work out the brackets first. A power or a root applies to the whole bracket, so (-4)² = 16, a positive number.

A fraction line is a division with brackets round the top and the bottom. Work out the numerator and the denominator separately, then divide.

Brackets make a calculation do its addition or subtraction first. To place one pair of brackets, try each addition or subtraction in turn.

Check by working the whole statement out in the correct order. Write one pair.

Subtracting a negative number is the same as adding: 5 - (-3) = 5 + 3. A negative times a positive gives a negative answer. A negative times a negative gives a positive answer.

To multiply by a decimal, work out 8 × 2 = 16, then put the decimal place back: 1.6. Put the sign on last.

Practical situations use the same rules. From 4°C down to -7°C is a fall of 4 - (-7) = 11°C.

Change mixed numbers to improper fractions first. Then write both fractions over a common denominator, and add or subtract the numerators only.

Give the answer in its simplest form. Do not subtract the denominators.

To multiply, multiply the numerators and multiply the denominators. Cancel common factors first if you can.

To divide, invert the second fraction and multiply. A whole number such as 5 is 5/1, so dividing by 5 means multiplying by 1/5.

In money problems, work out the calculation first, then think about what the answer means. "The greatest number that can be bought" means divide, then round down.

On the graphic display calculator, enter the division and read off the whole number part. Rounding up would give a number of items you cannot afford.