Students keep making the same mistakes in their GCSE Maths exams. Inspired by the examiner's reports find out where students are losing vital marks, so that you can avoid the common slip-ups!

# Calculator

It is vital that you get to know exactly how your calculator works so you don't waste unnecessary time in the exam. Don't rely on borrowing one as you **may not be familiar with it** (and you might annoy your maths teacher!).

Your calculator must be a **scientific **one and you should have an instruction booklet with it.

**Below is diagram of a calculator. Roll over each button to see what it does:**

For the rest of this section it might be handy if you have your calculator and instruction booklet close at hand.

Firstly, your calculator will do things in a certain order regardless of how you type them in.

For instance, 3 + 2 x 5 comes to 25.

Try typing it into your calculator (only pressing = at the end).

**Did you get the answer 13?**

If you did it's because your calculator will have worked out 2 x 5 first **then** added 3.

Your calculator operates what we call **BODMAS:**

This is the order in which it will do operations. **So be careful!**

**Avoid making mistakes by:**

**1.** Using the Memory function to store stages in your working out before using them again.

**2.** Using the Bracket buttons.

**3.** Pressing the '=' sign after each operation.

Find out where all these things are on your calculator! **Here's an example:**

**Work out...**

Now, you want everything on the top to be divided by 4.1 so you must press'=' after you have typed in the top of the fraction.

You can either work out the bracket first then add 5.8 or use the brackets on your calculator and type it straight in! You should get 8.7 for the top. Now divide it by 4.1 to get 2.12195122

**Try it!**

**Now try:**

You should get 3.564 (to 3 decimal places). If you didn't, try it again using the information above.

If you didn't, try it again using the information above.

**Did you put the bottom of the fraction in brackets or use the memory?**

Your calculator should have special buttons which 'square' and 'square-root'. Find out where they are!

However, sometimes you may need to find higher powers or roots and you have to use a different button for that. Here's what the buttons may look like (although they might be above other buttons so you have to use *Shift* or *2ndfn* to get to them):

As you can see from the example above, to do 2^{6}, type in 2, press your power button, type in 6 and press '='.

You should get 64.

To do the 4^{th} root of 81, type in 81, press your root button, type in 4 and press ?=?.

You should get 3.

If you can't get the answers above, consult your instruction book on how to do it on your machine as it might be different!

You can find out more about Standard Form in the section on **'Indices'**.

Your calculator Standard Form buttons will probably say **EXP** or **EE.** If you can't find this, have a look at your instruction book.

Now, as you should know, Standard Form is a number between 1 and 10 multiplied by 10 to a power. Your calculator may not indicate the 'x 10' bit. If it doesn't it will show the number then the power of 10 smaller and to the right.

Don't mistake this as meaning the power is for the number on the screen. It isn't. It's a power of 10!

The button EXP or EE means 'x 10^{?}' so to do 3.5 x 10^{8} you type 3.5, press EXP then type 8.

**You can now do arithmetic using Standard Form:**

* For example:* try (4.5 x 10

^{7}) x (3.1 x 10

^{9})

You should get 1.395 x 10^{17}

As you probably know, fractions are divisions and you can do them on your calculator by using the divide button.

However, your calculator will then work in decimals which are sometimes not as accurate and, anyway, we might need to write the answer as a fraction.

Most calculators will have their own fraction buttons. **They may look like this:**

They are incredibly useful for doing fraction work and may even change top-heavy fractions into mixed numbers and vice versa.

Learn how to use them and what the fractions look like on your screen.

**You can check you are OK by using the following examples if you wish -just type in the number you get in the space with a question mark:**