Question

1. in a chemistry class, the average age of 19 students is 16.21. a foreign exchange student is added a month after the class starts and is 17 years old. what is the new average age of the ap chemistry class? (a) 16.05 (b) 16.22 (c) 15.40 (d) 16.25 (e) 16.89

Explanation:

Step1: Find the sum of ages of 19 students

The formula for the average $\bar{x}=\frac{\sum_{i = 1}^{n}x_{i}}{n}$. Given $n = 19$ and $\bar{x}=16.21$, then $\sum_{i = 1}^{19}x_{i}=n\times\bar{x}=19\times16.21 = 307.99$.

Step2: Add the age of the new - student

The new sum of ages $\sum_{i = 1}^{20}x_{i}=307.99 + 17=324.99$.

Step3: Calculate the new average

The new number of students $n = 20$. The new average $\bar{x}=\frac{324.99}{20}=16.2495\approx16.25$.

Answer:

D. 16.25