Adding and Subtracting Three Decimals
To add or subtract decimals:
1. Write down the decimals, one under the other, with the decimal points lined up.
2. If the decimals have different numbers of digits, then fill in the blank spaces with zeros so that the decimals have the same decimal digits.
3. Add or subtract as usual from right to left, column by column.
4. Place the decimal point in the sum or difference, in line with the other decimal points.
For example: Let's add 14.26, 23.1, 32.33.
Notice that the decimal digits are not the same.
Let's write the decimals one under the other, with the decimal points lined up and add zeros so that the decimals digits become same.
1  4  .  2  6  
2  3  .  1  0  

3  2  .  3  3 
Now, add from right to left, column by column.
Place the decimal point in the sum, in line with the other decimal points.
1  4  .  2  6  
2  3  .  1  0  

3  2  .  3  3 
6  9  .  6  9 
So, the sum is 69.69.
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Help
The correct answer is
Remember :
The smallest number is the one that comes first while counting.
Solution :
To arrange the given numbers in order from smallest to greatest, find the smallest number among all the given numbers.
21,27,23
21 is the smallest number.