Hello, welcome to my blog, this is my summary assignment for Math Honours 9.

In this summary I will be explaining how to multiply and divide decimals. It will be shown step-by-step with tips along the way. There will be a word problem at the end for you to attempt by yourself.

Firstly, we will start with an easy problem.

Example 1. Multiplication of decimals  (Easy)             4.2 x 3.2

Step 1.   Arrange this question into the long multiplication method. I prefer this method but you are free to do whatever method you would like. For this example we shall do long multiplication.

       

Step 2. Begin by ignoring the decimals and multiplying as you normally would.

Tip: Don’t forget to add in the zero in the second row when working.

Step 3.  Add up your total.

Step 4. Count the decimal places behind the decimal of each number, then add it up.

(Ex. 2.14 has two decimal places and 3.1415236777322 has 13 decimal places.)

One decimal place + One decimal place = 2 decimal places.

Step 5. Add the amount of decimal places needed.

In this case, you need two decimal places, therefore the answer is…

 

13.44

Example 2. Multiplication of decimals (Hard)         39.8 x 12

Step 1.  Arrange this question into the long multiplication method. As before, you are allowed to choose which method you would like, but long multiplication is best for beginners.

Tip: Remember to line up the digits on the right and not according to the decimal point.

Step 2. Ignore the decimal for now and multiply as usual.

Step 3. Add the up the total

Tip: Remember to check your work

Step 4. Count the decimal places behind the decimal point and add it up.

Step 5. Place the decimal point where it belongs.

In this case you need one decimal place, therefore the answer is….

 

477.6

Example 3. Dividing Decimals (Easy)   2 divided by 4.84212

Step 1. Arrange this problem into the long division method like this.

Step 2. Divide then put the decimal point where it belongs.

Step 3.  Divide as normal until you get to the last two digits.

Step 4. In this step you will have to put a zero because 1 isn’t divisible by 2.

Your answer should turn out to be…..

 

2.42106

 

Practice Question: Dividing Decimals (Try on your own)

Four friends went out to dinner and spent 45.64$ in total. They split the cost evenly among them. How much did each friend pay?

 

 

 

 

 

Answer: 11.41

 

Thank you for reading my blog and I hope you learned something new today!