Question 1178715
Let's solve each problem step-by-step:

**Problem 1: Monthly Electric Bill**

* **Understanding the Issue:**
    * The mean monthly electric bill is given as ₱120.00.
    * The amounts ₱1,380 and ₱1,740 are extremely far from the mean, suggesting there might be an error in the problem statement. It's highly unlikely that monthly bills would be in those amounts.
    * To solve this problem, we need a standard deviation. Let's assume a standard deviation of ₱15.00.
* **Calculations:**
    1.  **Calculate z-scores:**
        * z1 = (1380 - 120) / 15 = 1260 / 15 = 84
        * z2 = (1740 - 120) / 15 = 1620 / 15 = 108
    2.  **Find probabilities:**
        * Because the z-scores are so high, the probability of the bill being in that range is extremely close to 0.
* **Answer:**
    * The probability is essentially 0.

**Problem 2: Mathematics Exam Scores**

* **Understanding the Issue:**
    * The exam scores are normally distributed.
    * Mean score (μ) = 25
    * Standard deviation (σ) = 5
    * We want to find the probability of scoring higher than 30.
* **Calculations:**
    1.  **Calculate the z-score:**
        * z = (X - μ) / σ = (30 - 25) / 5 = 5 / 5 = 1
    2.  **Find the probability:**
        * P(X > 30) = P(z > 1)
        * Using a z-table or calculator:
            * P(z < 1) ≈ 0.8413
            * P(z > 1) = 1 - P(z < 1) ≈ 1 - 0.8413 = 0.1587
* **Answer:**
    * The probability of scoring higher than 30 is approximately 0.1587, or 15.87%.