Step 1 : Put the digits according to the place value, that is one below the other,making sure that the decimals also exactly one below the other.
Ones below ones, tenths and so on.

Step 2 : Change the decimals to like decimals.

Step 3 : Add as usual. Start from the hundredths. Carry over if needed.

Step 4: Place the decimal point in the answer in the same place as the numbers above it.

Example : 2.37 + 3.8 = ?
 2.37 + 3.8 --------- 2.37 + 3.80 (like decimals) ---------- 6.17

1) Add : 23.11 + 3.8
Solution :
 23.11 + 3.80 --------- 26.91

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2) 23 + 18.94
Solution :
 23.00 + 18.94 --------- 41.94

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3) 162.1 + 16.21
Solution :
 162.10 + 16.21 --------- 178.31

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4) 13.8 + 124.56
Solution : First write the bigger number and below it according to the places of decimal write the 2nd number.
 124.56 + 13.80 --------- 138.36

Practice

1) 562.9 + 49.3
2) 0.1 + 1 + 11.60
3) 9 + 1.8
4) 9.85 + 0.61
5) 17.5 + 16.87

Q.2 Compare using >, <, or =
1) 5.72 + 3.80 ( ) 8.52
2) 2.5 + 3.09 ( ) 5.95
3) 61.2 + 5.31 ( ) 48.72 + 12.9
4) 10 + 0.01 ( ) 10.01
5) 3 + 0.05 ( ) 0.35

Introduction of Decimals

Expansion of decimals
Comparison of decimals