Addition and subtraction – balance equations – up to 100

key notes :

⭐ What is a Balance Equation?

  • A balance equation means both sides are equal (same value).
  • The equal sign (=) shows both sides are balanced.

👉 Example:

  • 25 + 15 = 40
  • 40 = 25 + 15 ✔️ (both sides are equal)

⚖️ Think of a Balance Scale

  • Imagine a balance scale ⚖️
  • If both sides have the same weight → it is balanced
  • If not → it is not balanced

➕➖ Using Addition and Subtraction

  • We use addition (+) and subtraction (−) to make both sides equal
  • Numbers are up to 100

👉 Example:

  • 30 + 20 = 50
  • 50 − 10 = 40

🔍 Find the Missing Number

  • Sometimes a number is missing (□ or ___)
  • We solve it to balance the equation

👉 Examples:

  • 25 + ___ = 60 → answer is 35
  • ___ − 15 = 45 → answer is 60

🔄 Check Both Sides

  • Solve each side separately
  • Compare the answers

👉 Example:

  • 20 + 30 = 40 + 10
  • Left side = 50
  • Right side = 50 ✔️ (Balanced)

❌ True or False

  • Decide if the equation is correct or not

👉 Examples:

  • 45 + 5 = 50 ✔️ (True)
  • 70 − 20 = 40 ❌ (False, correct answer is 50)

🧠 Tips for Students

  • Always calculate carefully
  • Use mental math or fingers if needed
  • Check your answer again
  • Keep numbers within 100

🎯 Learning Goal

  • Understand that both sides must be equal
  • Solve simple addition and subtraction equations
  • Find missing numbers easily

Learn with an example

👉 Which number makes the equation true?

32 + ____  = 81 − 13

  • First, subtract 81 − 13:
  • 32 + ? = 81 − 13
  • 32 + ? = 68
  • Decide which number makes the addition number sentence true. You can subtract to find the answer.
  • Subtract: 68 − 32 = 36
  • The missing number is 36.

👉 Which number makes the equation true?

64 − _____  = 7 + 7

  • First, add 7 + 7:
  • 64 − ? = 7 + 7
  • 64 − ? = 14
  • Subtract 14 from both sides:
  • 64 − ? − 14 = 14 − 14
  • 50 − ? = 0
  • Now, find the number that goes in the blank space. Remember, when a number is subtracted from itself, the difference is zero. The number in the blank space must be 50.
  • The missing number is 50.

👉 Which number makes the equation true?

99 − 87 =____  + 8

  • First, subtract 99 − 87:
  • 99 − 87 = ? + 8
  • 12 = ? + 8
  • Decide which number makes the addition number sentence true. You can think of an addition fact you know, or you can subtract to find the answer.
  • The addition fact is: 4 + 8 = 12
  • Did you remember this addition fact? If not, you can find the answer by subtracting.
  • Subtract: 12 − 8 = 4
  • The missing number is 4.

Let’s practice!🖊️