4.04 Percentages with technology

When working with larger or more complex numbers it can become tiresome to evaluate everything by hand and it is for this reason that we have digital technologies that can do this part for us. When using a calculator to solve percentage and decimal problems, there are a few buttons on the calculator that we will need to know about.

Inputting decimals

When inputting decimals into a calculator we use the  button. Using this button, we can input decimals by pressing this button after the ones digit and before the tenths digit.

For example, if we wanted to input $15.9$15.9 into the calculator, we would press the buttons in this order:

Inputting percentages

When converting percentage values into non-percentage values without a calculator, we would remove the $%$% symbol and then divide by $100$100. This method doesn't change when using a calculator, we just don't have to evaluate the division by ourselves.

There are also some calculators that have a  function which may be stored as an alternative command. On most calculators, this function has the same effect as dividing by $100$100.

For example, we can input $59%$59% into the calculator by pressing the buttons in this order:

If the calculator's  function acts as division by $100$100 then the output of this expression will be $0.59$0.59 or $\frac{59}{100}$59100​.

We can use this function to convert percentage values into non-percentage values by inputting them into the calculator as shown above and evaluating the expression.

Getting results from the calculator

Depending on the type of calculator, the result of a calculation will be expressed as either a decimal or as a fraction. To convert from a fraction to a decimal we can use the  button.

It should be noted that the calculator cannot give percentage values as outputs. In our working out we would usually multiply by $100%$100% to convert a non-percentage value into a percentage value. When using a calculator we need to break this up into two steps:

1. Multiply the non-percentage value by $100$100
2. Attach the $%$% symbol to the result when writing the answer

Practice questions

Question 1