Worksheet for practicing scientific notation operations, including addition and subtraction of numbers in scientific notation.

Let's solve each of these scientific notation operations step by step. The key idea is to convert numbers to the same power of 10 before adding or subtracting, then express the result in proper scientific notation.

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1. $ 2.9 \times 10^4 + 3.2 \times 10^4 $

Both have the same exponent: $10^4$

Add coefficients:
$$
2.9 + 3.2 = 6.1
$$
So,
$$
6.1 \times 10^4
$$

✔ Answer: $ \boxed{6.1 \times 10^4} $

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2. $ 1.11 \times 10^2 + 2.3 \times 10^4 $

Different exponents. Convert both to the same power. Let's convert $1.11 \times 10^2$ to $10^4$:

$$
1.11 \times 10^2 = 0.0111 \times 10^4
$$

Now add:
$$
0.0111 \times 10^4 + 2.3 \times 10^4 = (0.0111 + 2.3) \times 10^4 = 2.3111 \times 10^4
$$

✔ Answer: $ \boxed{2.3111 \times 10^4} $

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3. $ 1.8 \times 10^4 + 4.12 \times 10^2 $

Convert $4.12 \times 10^2$ to $10^4$:
$$
4.12 \times 10^2 = 0.0412 \times 10^4
$$

Add:
$$
1.8 + 0.0412 = 1.8412
\Rightarrow 1.8412 \times 10^4
$$

✔ Answer: $ \boxed{1.8412 \times 10^4} $

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4. $ 9.5 \times 10^5 + 6.2 \times 10^4 $

Convert $6.2 \times 10^4$ to $10^5$:
$$
6.2 \times 10^4 = 0.62 \times 10^5
$$

Add:
$$
9.5 + 0.62 = 10.12
\Rightarrow 10.12 \times 10^5
$$

But this is not scientific notation (coefficient must be between 1 and 10). Adjust:
$$
10.12 \times 10^5 = 1.012 \times 10^6
$$

✔ Answer: $ \boxed{1.012 \times 10^6} $

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5. $ 5.91 \times 10^4 + 6.12 \times 10^3 $

Convert $6.12 \times 10^3$ to $10^4$:
$$
6.12 \times 10^3 = 0.612 \times 10^4
$$

Add:
$$
5.91 + 0.612 = 6.522
\Rightarrow 6.522 \times 10^4
$$

✔ Answer: $ \boxed{6.522 \times 10^4} $

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6. $ 3.32 \times 10^6 - 4 \times 10^6 $

Same exponent: $10^6$

Subtract:
$$
3.32 - 4 = -0.68
\Rightarrow -0.68 \times 10^6
$$

Convert to scientific notation:
$$
-0.68 \times 10^6 = -6.8 \times 10^5
$$

✔ Answer: $ \boxed{-6.8 \times 10^5} $

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7. $ 7.32 \times 10^7 - 3.6 \times 10^6 $

Convert $3.6 \times 10^6$ to $10^7$:
$$
3.6 \times 10^6 = 0.36 \times 10^7
$$

Subtract:
$$
7.32 - 0.36 = 6.96
\Rightarrow 6.96 \times 10^7
$$

✔ Answer: $ \boxed{6.96 \times 10^7} $

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8. $ 4.2 \times 10^4 - 3 \times 10^2 $

Convert $3 \times 10^2$ to $10^4$:
$$
3 \times 10^2 = 0.03 \times 10^4
$$

Subtract:
$$
4.2 - 0.03 = 4.17
\Rightarrow 4.17 \times 10^4
$$

✔ Answer: $ \boxed{4.17 \times 10^4} $

---

9. $ 1.2 \times 10^2 - 2.3 \times 10^3 $

Convert $1.2 \times 10^2$ to $10^3$:
$$
1.2 \times 10^2 = 0.12 \times 10^3
$$

Subtract:
$$
0.12 - 2.3 = -2.18
\Rightarrow -2.18 \times 10^3
$$

✔ Answer: $ \boxed{-2.18 \times 10^3} $

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10. $ 2.02 \times 10^4 + 2.2 \times 10^5 $

Convert $2.02 \times 10^4$ to $10^5$:
$$
2.02 \times 10^4 = 0.202 \times 10^5
$$

Add:
$$
0.202 + 2.2 = 2.402
\Rightarrow 2.402 \times 10^5
$$

✔ Answer: $ \boxed{2.402 \times 10^5} $

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✔ Final Answers:

1. $ 6.1 \times 10^4 $
2. $ 2.3111 \times 10^4 $
3. $ 1.8412 \times 10^4 $
4. $ 1.012 \times 10^6 $
5. $ 6.522 \times 10^4 $
6. $ -6.8 \times 10^5 $
7. $ 6.96 \times 10^7 $
8. $ 4.17 \times 10^4 $
9. $ -2.18 \times 10^3 $
10. $ 2.402 \times 10^5 $

Let me know if you'd like a summary or explanation for any specific one!