Page 167 - Start Up Mathematics_6

Represent the decimal number 1.8 by shading 1 big
square and 80 small squares.

The sum of decimal numbers 2.13 and 1.8 is represented
by combining the shaded squares representing the two
decimals. The coloured part represents the sum as 3.93.

Verification: We can verify the result by directly adding the decimals
2.13
2.13 and 1.8 + 1.80
Note: Using the same method find the sum of decimals: 3.93
(a) 2.12 and 3.38 (b) 0.7 and 1.2.

Steps to Add Decimal Numbers
We use the following steps to add decimal numbers:

Step 1: Convert the given decimals to like decimals.

Step 2: Write all the decimal numbers one below the other keeping the decimal point as well
as the digits having the same place value in the same column.
Step 3: Add as we add whole numbers.

Step 4: In the sum, put the decimal point directly below the other decimal points.
Example 19: Find the sum in each of the following:

(a) 300.003 + 0.03 + 0.3 (b) 32.75 + 1.003 + 7.2
(c) 10.75 + 8.425 + 21 (d) 0.003 + 0.05 + 35

Solution: First convert given decimals into like decimals and then add.

(a) 300.003 (b) 32.750
000.030 01.003
+ 000.300 + 07.200
300.333 40.953

(c) 10.750 (d) 00.003
08.425 00.050
+ 21.000 + 35.000

40.175 35.053

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