MATHEMATICS CLASS NOTES: NURSERY THREE

TOPIC: ADDITION OF 2-DIGIT NUMBERS WITH REGROUPING (CARRYING OVER)

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1. COMPREHENSIVE CORE CONCEPTS

What is Addition?

Addition is a mathematical process where we put two or more numbers together to find out how many they are in total. We use the plus sign (+) to show addition and the equals sign (=) to show the answer.

In Nursery Three, we have already learned how to add small numbers like $5 + 2 = 7$. Now, we are moving to bigger numbers! These are called 2-digit numbers because they have two parts: the Tens and the Units.

Understanding Tens and Units (T & U)

Every 2-digit number has a "home."

• The Units (U) are the single numbers (0, 1, 2, 3, 4, 5, 6, 7, 8, 9). They live in the right-side room.
• The Tens (T) are groups of ten. They live in the left-side room.

For example, in the number 15, we have 1 Ten and 5 Units.

What is Regrouping (Carrying Over)?

Sometimes, when we add the numbers in the Units room, the answer is bigger than 9. But there is a rule: The Units room can only hold one digit (0 to 9).

If the answer is 10 or more, the "Ten" part is too big for the Units room. It must move (or be "carried over") to the Tens room to stay with its friends. This is what we call Regrouping.

Step-by-Step Guide to Adding with Regrouping

Let’s solve: 18 + 14

Step 1: Arrange the numbers vertically. Place Tens under Tens and Units under Units.

   T  U
   1  8
+  1  4
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Step 2: Add the Units first. Look at the Units column: $8 + 4$. Count 8 fingers/sticks, then add 4 more. You get 12. Wait! 12 is too big for the Units room. 12 is actually 1 Ten and 2 Units.

Step 3: Regroup (Carry Over). Write the 2 (the Unit) under the Units column. Take the 1 (the Ten) and carry it over to the top of the Tens column.

     1 (carried)
   T  U
   1  8
+  1  4
-------
      2

Step 4: Add the Tens column. Now add all the numbers in the Tens room, including the 1 we carried over: $1 (\text{carried}) + 1 + 1 = 3$. Write 3 under the Tens column.

   T  U
   1  8
+  1  4
-------
   3  2

Final Answer: 18 + 14 = 32.

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2. REAL-WORLD EXAMPLES

Scenario A: The Birthday Party Imagine you are at a birthday party. You have 17