MATHEMATICSOrder of Operations - BiDMAS

• The aim of this powerpoint is to teach you the order in which you undertake calculations involving two or more different operations.

EITHER

• Take notes as you go along, include some examples and write down any questions and your answers (which you can mark as you go along)

OR

• At the end of the powerpoint, printout the notes called Calc-9

BIDMAS• BIDMAS is an acronym to help us to remember in what

order we should undertake each operation when we have to solve a calculation involving mixed operations.

• B represents Brackets

• I represents Indices

• D & M represent Divide and Multiply

• A & S represent Add and Subtract

Worked Examples• Apply BIDMAS to calculate the answers to these:

1) 15 – 3 × 4 =

2) 8 + 24 ÷ 3 =

3) 9 × (15 – 6) + 5 =

4) 25 – (4 + 2²) × 2 =

Work out your answers before checking them on the next slide…

Example 11) 15 – 3 × 4 =

This calculation involves Subtract and Multiply

The order in BIDMAS tells us to do the multiply bit first so…

Replace the 3 × 4 with its answer of 12

Now we have: 15 – 12 = 3

Example 22) 8 + 24 ÷ 3 =

This calculation involves Add and Divide

The order in BIDMAS tells us to do the divide bit first so…

Replace the 24 ÷ 3 with its answer of 8

Now we have: 8 + 8 = 16

Example 33) 9 × (15 – 6) + 5 =

This calculation involves Multiply, Subtract in Brackets and Add

The order in BIDMAS tells us to do the brackets bit first so…

replace the (15 – 6) with its answer of 9

Now we have: 9 × 9 + 5

BIDMAS now tells us to do the multiply bit next so…

Replace the 9 × 9 with its answer of 81

Now we have: 81 + 5 = 86

Example 44) 25 – (4 + 2²) × 2 =

This calculation involves Subtract, Add & Indices in Brackets and Multiply

The order in BIDMAS tells us to do the bit in brackets first…

doing the indices bit before the add bit so…

replace the 2² with its answer of 4 which gives us (4 + 4) in brackets

to be replaced by its answer of 8

Now we have: 25 - 8 × 2 and BIDMAS tells us multiply first so…

replace the 8 × 2 with its answer of 16

Now we have: 25 - 16 = 9

Order

• Did you notice that although the order we complete bits of the calculation changes…

• We do NOT change the order in which they are written within the calculation so…

• In 8 – 2 × 3, although we do the 2 × 3 bit first, it appeared as the second half of the calculation and so its answer appears after the 8 and not before it.

• i.e. 8 – 6 NOT 6 – 8! 8 – 6 = 2P (6 – 8 = – 2 O)

Fractions

• Mixed calculations may also occur in the form of divisions written in fractional form.

• Remember to evaluate the whole of the top (using BIDMAS)

• Next evaluate the whole of the bottom (using BIDMAS)

• Only divide the top value by the bottom at the end

Example

• Work out the answer to this calculation before moving to the next slide to check…

29 – 24 ÷ (3 x 4)

5² – 4²

Answer

29 – 24 ÷ (3 × 4)

5² – 4²

TOP: BIDMAS 29 – 24 ÷ 12

BIDMAS 29 – 2 = 27

BOTTOM: BIDMAS 25 – 16 = 9

Fraction line says: Divide the top by the bottom so…

27 ÷ 9 = 3

What next?• If you haven’t made notes and copied examples,

questions and answers during this powerpoint, print out the notes called Calc9. Read through the notes and make sure you answer any questions.

• Work through the MyMaths lesson (and then the online homework) called Order of Operations found at: http://app.mymaths.co.uk/203-resource/order-of-operations

• http://app.mymaths.co.uk/203-homework/order-of-operations

• Complete the worksheet called BIDMAS-S1.xlsx

• Now move on to the Calc10a-Problems powerpoint