MATHEMATICS Using a Calculator – The Basics

The aim of this powerpoint is to teach you techniques for using scientific calculators to solve complicated calculations. 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-10

The basics Every calculator has the following signs: +ADD – SUBTRACT ×MULTIPLY (but on a computer this is an asterisk, i.e. *) ÷DIVIDE (but on a computer this is a slash sign, i.e. /) =EQUALS Most calculators also have the following signs: ²SQUARE √SQUARE ROOT π PI

Other keys… Scientific calculators also have: x y or xa power button x √y orx 1/y a root button EXPor× 10 x a standard form button ± or(–) to enter a negative number logand/or lna logarithm button S↔Da fractions ↔ decimals button sin, cos & tantrigonometric function keys Look out for the second function or inverse button which changes the operation of the button being pressed to the operation indicated above that button.

DAL or not? Most scientific calculators now have direct logic input This means that you can enter a calculation in the order that it is given and the calculator will work out the answer by applying BIDMAS for you. If you do not have a direct logic calculator, you will either need to insert extra sets of brackets (if you have these available on your calculator) or use BIDMAS and work out the answer to the calculation step-by-step

Example To solve: 6 + 7² – 42 Using a DAL calculator you would enter this in the order provided by hitting the following buttons: x² – 4 2 = On a non-DAL calculator which has brackets available, you would need to insert brackets to tell it to do the index bit first: 6 + ( 7 x² ) – 4 2 = On an ordinary calculator with no brackets you would do: 7 x² = (which would give an answer of 49). You would then clear the screen and enter: – 4 2 = The answer would be 13.

Interpreting the Answer The key to successfully using a calculator is two-fold… 1) Knowing how to use YOUR own calculator 2) Knowing how to interpret the answer it displays Remember… Time hours & minutes are not denary conversions Money in £ MUST be quoted EXACTLY to 2 d.p.

Interpreting Time Answers 10 friends have to share a 24 hour shift of guarding their Monarch. For how long (in hours and minutes) must each of them guard the queen? Calculation: 24 ÷ 10 = 2.4 Common Error: 2 hours 4 minutes Remember: 0.4 hrs  0.4 lots of 60mins = 24mins Correct Answer:2 hours 24 minutes

Interpreting Money Answers Three girls wish to buy some shampoo. Boots have a buy two get one free offer so the girls decide to share the cost of the two bottles of shampoo between the three of them. If one bottle costs £1.45 how much do they each pay? 2 bottles = 2 × £1.45 = £2.90 shared by 3 so… Calculation is:(2 × 1.45) ÷ 3 = Money (in £) is to 2 d.p. = £0.97

Estimating Answers As mentioned throughout the whole of this module of work, before accepting whatever answer you have calculated on paper or using a calculator, check it makes sense using a ‘rounded’ estimate. Work through the MyMaths lesson (and its online homework) called Estimating Introduction found at: Work through the MyMaths lesson (and its online homework) called Estimating Calculations found at:

What next? If you haven’t made notes and copied examples, questions and answers during this powerpoint, print out the notes called Calc10. Read through the notes and make sure you answer any questions. Work through the MyMaths ‘boosters’ online worksheet called Calculators – OW found at: You now need to revise everything you have done this module and create an A4 revision sheet, then your teacher will ask you to undertake the end of module assessment.