To calculate the overall percentage change of the stock, we can treat each percentage change sequentially, compounding them step by step.

Let's define the initial value of the stock as $P_0 = 100$ (using 100 for simplicity, as it allows us to easily compute percentages).

1. First week: The stock increased by 5%. $P_1 = P_0 \times (1 + 0.05) = 100 \times 1.05 = 105$

2. Second week: The stock increased again by 5%. $P_2 = P_1 \times (1 + 0.05) = 105 \times 1.05 = 110.25$

3. Third week: The stock dropped by 10%. $P_3 = P_2 \times (1 - 0.10) = 110.25 \times 0.90 = 99.225$

Finally, the overall percentage change from the initial value is calculated as: $\text{Overall change} = \left( \frac{P_3 - P_0}{P_0} \right) \times 100 = \left( \frac{99.225 - 100}{100} \right) \times 100 = -0.775\%$

So, the overall percentage change is approximately $-0.775\%$, indicating a slight decrease.

Would you like more details or have any questions?

Here are some related questions:

1. What is the importance of compounding in percentage changes?
2. How would the result differ if the stock had a different sequence of percentage changes?
3. What happens if there is an increase or decrease larger than 100%?
4. How do repeated percentage increases or decreases affect a stock over a long period?
5. Can percentage changes be directly added or do they require compounding?

Tip: When dealing with percentage changes, always apply them sequentially (not simply adding or subtracting), as each new percentage is applied to the updated value!