Instructions
Welcome, Code Breaker! Your mission is to find the missing number in each math problem. When you find the missing number, you are balancing the equation. Remember, the equals sign (=) means both sides must have the same value!
- Read each equation carefully.
- Use addition or subtraction to figure out the value of the missing number, represented by [N].
- Write your answer clearly in the space provided.
- Complete the Challenge section only after finishing the main problems.
Section 1: The Basic Code (Finding the Missing Part)
Find the value of [N] in each equation.
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$8 + [N] = 15$ [N] = $\underline{\hspace{4cm}}$
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$[N] + 12 = 20$ [N] = $\underline{\hspace{4cm}}$
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$25 - [N] = 10$ [N] = $\underline{\hspace{4cm}}$
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$[N] - 9 = 21$ [N] = $\underline{\hspace{4cm}}$
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$33 + 7 = [N]$ [N] = $\underline{\hspace{4cm}}$
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$50 - [N] = 25$ [N] = $\underline{\hspace{4cm}}$
Section 2: Balancing the Scales
For these problems, you must make sure the left side of the equals sign equals the right side. Solve the known side first, then find [N].
Example: $7 + 3 = 6 + [N]$. (Since $7+3=10$, you need $6 + [N]$ to also equal 10. [N] = 4.)
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$10 + 4 = 15 - [N]$ [N] = $\underline{\hspace{4cm}}$
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$22 - 2 = 18 + [N]$ [N] = $\underline{\hspace{4cm}}$
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$5 + 5 + 5 = 10 + [N]$ [N] = $\underline{\hspace{4cm}}$
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$30 - 5 = [N] + 10$ [N] = $\underline{\hspace{4cm}}$
Section 3: Real-World Missing Numbers
Use the table below to track how much money you still need to earn for a desired item. [N] is the amount still needed.
| Item | Total Cost | Money Saved | Amount Still Needed [N] |
|---|---|---|---|
| Example: Toy Car | $15 | $8 | $7 (Because $15 - 8 = 7$) |
| Video Game | $40 | $25 | |
| New Book | $18 | $11 | |
| Art Set | $35 | $15 | |
| Pet Supplies | $29 | $20 |
Section 4: The Master Challenge (Optional)
These problems require careful thinking and often two steps. Only attempt if you have finished all previous sections.
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$2 imes 5 + [N] = 20$ [N] = $\underline{\hspace{4cm}}$
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If a store had 15 apples and sold 6, then bought a new box of [N] apples, and now has 30 total apples, how many apples were in the new box? (Hint: Start with the amount they had after selling.) [N] = $\underline{\hspace{4cm}}$
Answer Key
Section 1: The Basic Code
- $8 + [N] = 15$ -> [N] = 7
- $[N] + 12 = 20$ -> [N] = 8
- $25 - [N] = 10$ -> [N] = 15
- $[N] - 9 = 21$ -> [N] = 30
- $33 + 7 = [N]$ -> [N] = 40
- $50 - [N] = 25$ -> [N] = 25
Section 2: Balancing the Scales
- $10 + 4 = 14$. $15 - [N] = 14$. -> [N] = 1
- $22 - 2 = 20$. $18 + [N] = 20$. -> [N] = 2
- $5 + 5 + 5 = 15$. $10 + [N] = 15$. -> [N] = 5
- $30 - 5 = 25$. $[N] + 10 = 25$. -> [N] = 15
Section 3: Real-World Missing Numbers
| Item | Total Cost | Money Saved | Amount Still Needed [N] |
|---|---|---|---|
| Video Game | $40 | $25 | $15 |
| New Book | $18 | $11 | $7 |
| Art Set | $35 | $15 | $20 |
| Pet Supplies | $29 | $20 | $9 |
Section 4: The Master Challenge
- $2 imes 5 = 10$. $10 + [N] = 20$. -> [N] = 10
- $15 - 6 = 9$ (apples left). $9 + [N] = 30$. -> [N] = 21