Using a calculator

BODMAS/BIDMAS on a calculator

BODMAS or BIDMAS must also be used when using a calculator. Scientific calculators automatically apply the operations in the correct order, however extra brackets may be required.

Example

Consider this calculation:

\frac{2 + 4}{10 - 7}

If 2 + 4 \div 10 - 7 was entered on a calculator, the calculator would use BODMAS/BIDMAS and calculate 2 + \frac{4}{10} - 7. The division would be completed before the addition or subtraction. This would give the wrong answer.

To make sure the calculation is correct, use the fraction button on the calculator or use brackets:

\frac{2 + 4}{10 - 7} or (2 + 4) \div (10 - 7)

Calculating indices on a calculator

On a calculator, brackets must be used when raising negative numbers to a power.

For example, to calculate -2 squared on a calculator, type in (-2)^2. This would give the correct answer of 4. If brackets were not used, BODMAS/BIDMAS would be applied and the answer given would be -4, as the power is applied before the subtraction.

Example

Find the value of x^2 + 7 when x = -3.

Using BODMAS/BIDMAS, the answer is calculated as:

  1. (-3)^2 = 9 (power/indices first)
  2. 9 + 7 = 16 (addition)

On a calculator, typing -3^2 + 7 gives an answer of -2 as the calculator does not automatically understand that the minus sign relates to a negative number, rather than a subtraction.

To get the correct answer, include extra brackets. Typing (-3)^2 + 7 into a calculator gives an answer of 16, which is correct.

curriculum-key-fact
When using calculators, place brackets around negative numbers before raising them to a power.