Module 1 Topic F Lesson 13/14

Module 1 Topic F Lesson 13/14

Dividing with Decimals Part 1

Important Lesson Vocabulary

• Division: breaking a number up into equal-sized groups

• Dividend: a number that you divide

• Divisor: a number that you divide by

• Quotient: the answer to a division problem

• Remainder: how much you have left over at the end of a division problem when you cannot make any more groups

 $20\ \div\ 5\ =\ 4$  

At the right I have 20 circles. I want to divide them by 5 (put them into groups of 5). I can model this by putting them in rows, with 5 in each row. I will be able to make 4 rows. 

So my answer is 4; I can make 4 groups of 5 with 20 circles. 

Consider the problem:

 $3.5\ \div\ 5$  

How could I divide 3 ones and 5 tenths into groups of 5 ones? 

Let's convert 3.5 to something we can work with!

• First I will change it to unit form: 3.5 = 3 ones and 5 tenths

• Next I will unbundle my 3 ones into 30 tenths, for a total of 35 tenths. Now I have

   $35\ tenths\ \div\ 5$  

At the right is an array representing 35 tenths in groups of 5. We were able to make 7 rows.

So our answer to the problem is 7 tenths.

 $3.5\ \div\ 5\ =\ 35\ tenths\ \div\ 5\ =\ 7\ tenths$  

Now we simply have to convert our 7 tenths back to standard form to get our final answer: 0.7

To Recap, for a problem like

 $4.2\ \div\ 6$  

• Convert your decimal to unit form: 4.2 = 42 tenths

• How many groups of 6 can you make with 42 tenths? In this case, you can make 7 groups of 6, so your answer is 7 tenths

• Convert your answer back to standard form: 7 tenths = 0.7