Multiplying by 10-Counting Zeroes With Decimals-Beginner-Lesson 1

Multiplying by 10-Counting Decimals-Beginner-Lesson 1

by Ann Hartter

​How are these the same?

​

Place value

​You can see in the top set that there is

a number with a 1 in the hundreds place,

a number with a 1 in the tens place,

and

a number with a 1 in the ones place.

Place value

In the bottom set, there is a decimal point.

​

​In the top number, the 1 is in the ones place. That's one dollar.

​

​So what are the other places called?

​Let's start with $0.10

This is ten cents.

A ten cent piece is called a dime. ​

​There are ten dimes in one dollar.

​That means if you take a dollar and break it into 10 parts, you have a dime.

​

(Not for real, please don't break your paper dollar bills. That will make it worth $0)

$0.10

Since a dime is one of ten pieces of a dollar, and you have one of them, then you have one tenth of a dollar.

​

​we call this place the ​tenths place

Tens or Tenths?

​

What is the difference between the tens place and the tenths place?

​

• ​the th sound

• ​the decimal point

• ​one is 10 times bigger than the ones place (add a zero) and the other is 10 times smaller than the ones place (subtract a zero?)

​Counting decimal places

​Each decimal place is a "zero."

​

​

​

Divide by 10s​

​One dollar divided by ten is ten cents.

​

​Pay special attention to the

​decimal--the dot between

the dollars and cents.

​

​You could say that the decimal point moved.

​

​In fact, it's very common for mathematicians to say "move the decimal point."

​Dividing by 10

1 divided by 10

​

​is like saying

​Make this number smaller

​by 10

​

​So if you count how many zeroes are in 10, and then "move the decimal point"

​

​wait! where is the decimal point on the 1?

Where is the decimal point?

​Remember when you had just one dollar? There were no cents.

​

​That's how all numbers work.

​

​There are always zero parts of the whole hanging out behind the whole number.

​

​We just don't write the decimal unless we're going to use it.

​Dividing by 10

1 divided by 10

​

​is like saying

​Make this number smaller

​by 10

​

​So if you count how many zeroes are in 10 (one zero) and then "move the decimal point" to make one zero, then you have one tenth.

​Dividing by 100?

1 divided by 100

​

​is like saying

​Make this number smaller

​by 100

​

​So if you count how many zeroes are in 100 (two zeroes) and then "move the decimal point" to make two zeroes, then you have one hundredth.

• ​Remember the th from tenth?

What is one hundredth

One hundred is 100,

​one hundredth is 0.01.

​

multiply 1 x 100 = 100

divide 1 ÷ 100 = 0.01

​

​There are still two zeroes!

​What is one hundredth of a dollar?

The penny!

​

​If you broke your dollar into 100 pieces (again, please do not break your paper money) then you would have one hundredth of a dollar.

​Review

Place value

​

​Hundreds

​Tens

​Ones

Tenths

​Hundredths

​Bonus

You can further divide a dollar into 1,000 pieces. They only do this for counting taxes, and there are no coins for this tiny of a measure.

​

​The place value is called a thousandth.

​

​The coin, if we had one, would be called a mill.