Session 5: Adding Decimals – Steps, Interactive and Examples

The decimal system lets us represent numbers that are less than one and other numbers that exist between whole numbers. In a decimal number, the decimal point divides the whole part of the number from the decimal part of the number.

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Adding Decimals

The addition of decimal numbers is as simple as whole numbers. The only difference is we need to ensure the decimals of given numbers are lined perfectly.

Steps to Add Decimals

To add decimal numbers, we use the following steps:

Step 1: Convert the given decimals into like decimals.

Step 2: Arrange the numbers vertically to line up the decimal points.

Step 3: Add from right to left, carrying just as if you were adding whole numbers.

Step 4: Insert a decimal point into your answer to line up with the decimal points of the original numbers.

1) Find the sum of 51.22, 6.485 and 15.

Converting the given decimals to like decimals, we have 51.220, 6.485 and 15.000.

Now, we arrange the numbers vertically to line up the decimal points. 

Next, add from right to left. Start by adding 0, 5 and 0 to make 5. Then, add 2, 8 and 0 to make 10. Carry the 1 and add it with 2 and 4 to make 7. Now add 1, 6 and 5 to make 12. Carry the 1 and add it with 5 and 1 to make 7. Insert a decimal point into your answer directly under the decimal points in the original number. 

The answer is 51.220+6.485+15=72.705.

Adding Decimals – Examples

Example 1

Add the decimals78.12 and 96.54.

We arrange the numbers vertically to line up the decimal points.

Next, we add the digits from right to left and insert a decimal point directly under the decimal points of the original numbers.

Example 2

Add the decimals: 987.127, 1243.552 and 139.743.

We arrange the numbers vertically to line up the decimal points.

Next, we add the digits from right to left and insert a decimal point directly under the decimal points of the original numbers.

The answer is 987.127+1243.522+139.743=2370.922

Example 3

Add the decimals: 7439.248, 527.39, 74.172 and 38.

Converting the given decimals to like decimals, we have 7439.248, 527.390, 74.172 and 38.000.

Now we arrange the number vertically so that the decimal points line up. Next, we add the digits from right to left. 

The answer is 7439.248+527.39+74.172+38=8078.810.

Example 4

A dry fruit store sold 54.236 kg of almonds, 37.129 kg of walnuts and 26.828 kg of cashews in one day. What is the total weight of the nuts sold that day?

The total weight of the nuts sold that day is the sum of the weights of the almonds, walnuts and cashews.

We arrange the numbers vertically to line up the decimal points. 

Next, we add the digits from right to left and insert a decimal point directly under the decimal points of the original numbers. 

The total weight of the nuts sold in the store that day is 118.193 kg.

Example 5

A runner took 37.2071 seconds to run the first round of a race. He then completed the second and third rounds in 39.828 seconds and 36.54 seconds. What is the total time taken by the runner to complete the race?

The total time taken by the runner to complete the race is the sum of the time taken by him to complete the first, second and third rounds of the race. 

Converting the given decimals to like decimals, we have 37.2071, 39.8280 and 36.5400.

We arrange the numbers vertically to line up the decimal points. 

Next, we add the digits from right to left and insert a decimal point directly under the decimal points of the original numbers. 

The runner took 113.5751 seconds to complete the race. 

Example 6

Preeti travelled 62 km 45 m by car, 210 km 854 m by bus and the rest of 890 m she walked. How much distance did she travel in all?

Distance travelled by car = 62 km 45 m = 62.045 km

Distance travelled by bus = 210 km 854 m = 210.854 km

Distance travelled on foot = 0.890 km

∴ Total distance travelled by Preeti = 62.045 km + 210.854 km + 0.890 km

                                                            = 273.789 km

Remember this!

To add decimal numbers, we use the following steps:

Step 1: Convert the given decimals into like decimals.

Step 2: Arrange the numbers vertically to line up the decimal points.

Step 3: Add from right to left, carrying just as if you were adding whole numbers.

Step 4: Insert a decimal point into your answer to line up with the decimal points of the original numbers.