Operations with whole numbers with technology
Technology can make doing mathematical operations quicker and easier, but there are some common mistakes and pitfalls to keep in mind.
The most common type of technology used for performing operations is the hand-held calculator, so let's run through the basics.
The buttons we will use at the moment are:
To perform an operation between two numbers with your calculator,
- Press the buttons corresponding to the digits of the first number going from left to right
- Press the corresponding operation button
- Enter the second number the same way as the first
- Press the equals sign
The answer should now appear on the calculator display.
To evaluate an expression involving more than one operation we need to pay attention to the order of operations . We always evaluate inside parentheses first and, working from left to right, do any multiplication or division before addition or subtraction. If you enter the expression exactly as it appears in the question, your calculator will automatically do the correct order of operations.
Sometimes it may be quicker to break up the expression and do each operation separately. To do this, perform each operation then press the " = " button, respecting the order of operations. The answer each time you press equals becomes the 'first number' that you can then perform further operations on.
It's always useful to check the reasonableness of your answer. If the answer doesn't seem right, there's a good chance it isn't.
There are many mistakes that can occur when using your calculator, here are some common ones:
Not using the correct order of operations
Missing a digit from a number
Swapping the digits in a number
Swapping numbers in the expression
Using the wrong operation
Adding an extra digit
Calculators are useful as long as they are used correctly and mistakes are avoided. Even so, you should always keep in mind that it might just be quicker and more reliable to work it out in your head or on paper.
Examples
Example 1
Use a calculator to evaluate 214+443.
Example 2
Using a calculator, evaluate 47-(14+(14\div7 )).
Example 3
Xavier used his calculator to evaluate 16 \times 85 -2 and got the answer 926.
Is Xavier's answer correct?
What mistake might Xavier have made when he entered the expression into his calculator?
The buttons we need to use on our calculators are:
It's always useful to check the reasonableness of your answer. If the answer doesn't seem right, there's a good chance it isn't.