BestMaths Online

Calculators and Spreadsheets

Computers and calculators are being used more and more by students, teachers and workers to help solve problems quicker. Calculators can do many more types of calculations now than just a few years ago. For example, calculators can draw graphs, do algebra and carry out most statistics calculations.

Although calculators can do many types of calculation, at primary and lower secondary levels you should be able to do all of the operations in the ten topics covered so far WITHOUT using computers and calculators. Calculators are useful tools for checking your answers.

This section shows you how to do some of those calculations using these tools.

Calculators

A Casio graphical calculator

Try not to use your calculator for simple calculations involving adding, subtracting, dividing and multiplying whole numbers and integers . e.g. 8 × 7 or -6 + 2. Keep the instruction booklet that comes with the calculator. You may need it for the more complicated calculations and functions. Estimate the answer to the calculation before you start. This is a good check in case you press the wrong keys.

There are many makes and types of calculators. The examples below use keys from the Casio fx-82TL which are common or similar to most calculators.

Basic Operations

Enter the numbers in the order they are given, then press 

Type of calculation	Examples	Calculator Keys
Adding	35 + 739	774
Subtracting	965 − 349	616
Multiplying	59 × 38	2242
Dividing	3510 ÷ 78	45

BEDMAS

Calculators know about the order that calculations are carried out. i.e. BEDMAS

e.g. Calculate 56 + 3 × 85 on a calculator. Press:         311

---

Integers

 

Integer calculations are done using the  key for the negative integers.

Examples	Calculator Keys
5 + - 6	-1
-3 × -2	6

Rounding

Some calculators do not round numbers. e.g.    gives 0.666666666. This is calledtruncating.

Some calculators round numbers up or down e.g.    gives 0.666666667. This is calledrounding.This number is rounded to 9 decimal places as there are 9 digits after the decimal point.

Rounding Rules

If the digit to the right of the rounded digit is between 0 and 4.	The rounded digit stays the same.
If the digit to the right of the rounded digit is 5 or above.	The rounded digit has ONE added.

---

Square roots

 

To find the square root of a number use this key  e.g. To find the square root of 36, press    6

Square roots are often not whole numbers e.g.     6.08276253

---

Fractions

 

Some calculations involving fractions can be done on a calculator.

Fraction calculation	Example	Calculator Keys
Change a fraction to a decimal.	Write 5⁄8 as a decimal	0.625
Change an improper fraction to a mixed number.	Write 15⁄4 as a mixed number	334 This is 33⁄4
Do fraction calculations (see Topic 49)	Calculate 1⁄4 + 5⁄8	7 8 This is 7⁄8

Percentages

Most calculators have a  key. On some calcualtors this means pressing the  key first.

Use these keys to write a fraction as a percentage.

e.g.      62.5

Brackets

The two brackets keys  and  are useful for calculations involving more complicated fraction calculations.

e.g. Calculate  Press:            0.351894736

---

Indices

 

There is a button for an index of 2 (squared)  e.g. To find 14², press     196

To calculate with an index greater than 2 use the button  e.g. To find 2⁴, press     16

---

 

Spreadsheets 

Computer programs such as Microsoft Office and Appleworks include a part called aspreadsheet. 
Spreadsheets can perform calculations using numbers and formulae arranged in rows and columns of cells. 
Words or numbers can be typed into the cells and calculations and other mathematical operations can be carried out. 
Other units in MathsOnline will contain spreadsheet exercises indicated by 

The spreadsheet on the left shows only 32 cells. Some spreadsheets have thousands of cells. Each cell has its own label.  The one highlighted is cell B3. The letters are at the top of the columns. The numbers are at the beginning ofrows. To move around a spreadsheet use the cursor or keys such as the TAB, pg up, pg down (the arrow keys)

Many features of a spreadsheet can be changed (formatted) using various menu commands:

• The columns can be made wider
• The rows can be made higher
• Numbers and text in a cell can be made bold, coloured or a different size and font
• Numbers and text in a cell can be put on the left hand side, the right hand side or in the centre.

Calculations

Spreadsheets do calculations differently from normal maths equations and calculators. To do a calculation you have to type in the EQUALS sign first. To do multiplication use the * key and for division use the / key.

 

Formulae

The values in cells can also be used in calculations.

Sorting

Numbers and words in both rows and columns can be sorted into order.
To do the sort shown below BOTH columns must be selected and the spreadsheet told to sort on the B column.

Graphing

Most spreadsheets will produce graphs, such as pie graphs, line graphs, bar graphs and scattergraphs.
See Unit 44 for instructions and practice with these.