Core Connections: Course 2
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1. Section 4.1
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Exercise 20 Page 195

Practice makes perfect
To find the product, we multiply just like we do with two whole numbers. We will ignore any decimal points for now.
Applet to multiply two natural numbers
Now we place the decimal point in the product by counting the number of decimal places in each factor.
multiplication
The product of 4.76 and 12.5 is 59.500, or simply 59.5.
To add decimals, we line up the decimal points so that place-value positions match. We will add a zero to the first number so that each place has a digit.
decimal points aligned
Now we add the decimals just like we would with whole numbers. We will then place the decimal point in the answer.
45+6+23.68=69.28
The sum is equal to 69.28.
To subtract decimals, we line up the decimal points so that place-value positions correspond. Remember to add zeros as necessary so that each place has a digit.
decimal points aligned
Now we subtract the decimals just as we would with whole numbers and place the decimal point in the answer.
subtraction
The difference is 35.38.
To find the product, we multiply just like we would with two whole numbers. Ignore the decimal points for now.
Applet to multiply two natural numbers
Now we place the decimal point in the product by counting the number of decimal places in each factor.
multiplication
The product of 10 and 0.034 is 0.340, or simply 0.34.
To subtract decimals, we line up the decimal points so that place-value positions correspond. Remember to add zeros as necessary so that each place has a digit.
decimal points aligned
Now we subtract the decimals just as we would with whole numbers and place the decimal point in the answer.
subtraction
The difference is 134.12.

We want to simplify the given expression. 13.6+23.05+0.781 Let's start by adding 13.6 and 23.05. We line up the decimal points so that place-value positions match and add zeros as necessary so that each place has a digit.

decimal points aligned
Now we add the decimals just like we would with whole numbers and place the decimal point in the answer.
13.60+23.05=36.65
The sum of 13.6 and 23.05 is 36.65. Let's rewrite our expression. 13.6+23.05+0.781=36.65+0.781 Next, we add 36.65 and 0.781. Line up the decimal points and add zeros as necessary.
decimal points aligned
Now add the decimals and place the decimal point in the answer.
36.65+0.781=37.431
The sum of 36.65 and 0.781 is equal to 37.431.