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Math help from the Learning Centre

This guide provides useful resources for a wide variety of math topics. It is targeted at students enrolled in a math course or any other Centennial course that requires math knowledge and skills.

Decimal Notation

The dot represents a decimal point where place values are separated by what is to the left and right. To the right of the decimal points such as a tenth \(\frac{1}{10}\), a hundredth \(\frac{1}{100}\), and so on. 


Name the following numbers:

1) \(203.65\) = Two hundred three and sixty-five hundredths

2) \(2.008\) = Two and eight thousandths

Write out the following numbers:

1) One thousand twenty-two and three tenths = \(1022.3\)

2) Eighty thousand and eighty thousandths = \(80,000.080\)

Converting Between Fractions and Decimals

The decimal place value determines how to convert a decimal into a fraction.

For example, \[0.045\] 

ends at the thousandths place value. Therefore you put the number over 1000


Simplify the fraction


See video below for more examples, including mixed fractions and converting from fractions back to decimals.


Rounding Decimal Notation

To round to a certain place:

  1. Locate the digit in that place.
  2. Consider the next digit to the right.
  3. If the digit to the right is 5 or greater, round up; if the digit to the right is 4 or lower, keep digit the same. 


1. Round \(0.084\) to the nearest tenth.


Locate the digit in the tenths place


Consider the next digit to the right, 8

Since 8 is greater than or equal to 5, round up.


2. Round \(212.5604\) to the nearest hundredths


Locate the digit in the hundredths place


Consider the next digit to the right, 0

Since 0 is 4 or lower, keep digit the same.


Decimal Arithmetic Operations

Example 1: Find the total resistance for the circuit diagram below. The total resistance of a series circuit is equal to the sum of the individual resistances.


The total resistance is the sum of the individual resistances in this series circuit.


Example 2: A series circuit containing two resistors has a total resistance (\(R_T\)) of 37.272 ohms. One of the resistors (\(R_1\)) has a value of 14.88 ohms. What ist eh value of the other resistor (\(R_2\))?


We have to subtract \(R_1\) from the total resistance \(R_T\).


Example 3: Using the formula Watts = Amperes \(\times\) Voltage, what is the wattage of an electric drill that uses 9.45 amperes from a 120 volt source?


We need to multiple 120 amperes by 9.45 volts to find the wattage of the electric drill.

\[120\times 9.45=1134\,watts\]

The electric drill is 1134 watts.

Example 4: 500 g of potatoes costs $3.50. How much do potatoes cost per gram?



Potatoes cost $0.0068/g

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Designed by Matthew Cheung. This work is licensed under a Creative Commons Attribution 4.0 International License.
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