The problem is in Chinese and translates as follows:

Currently, the average age of five friends is 10.4 years. What will the average age be in three years?

Options:

1. $A$: No change
2. $B$: Increase by 0.6 years
3. $C$: Increase by 3 years
4. $D$: Cannot be determined

Solution

The current average age of the five friends is 10.4 years. This means the total of their ages is: $10.4 \times 5 = 52 \text{ years}$

After three years, each friend's age will increase by 3 years, so the total increase in their combined ages will be: $5 \times 3 = 15 \text{ years}$

Thus, the new total age will be: $52 + 15 = 67 \text{ years}$

Now, the new average age after three years will be: $\frac{67}{5} = 13.4 \text{ years}$

So the average age increases by: $13.4 - 10.4 = 3 \text{ years}$

Answer:

The correct answer is $C$: Increase by 3 years.

Would you like a more detailed explanation, or do you have any questions?

Related Questions

1. What would be the average age in five years?
2. If one more friend, aged 12, joins the group, how would it affect the average age?
3. How do changes in the number of people in a group affect the average?
4. What is the effect on the average if only three of the five friends grow older by three years?
5. How would the average age change if two of the friends were younger than the others?

Tip

Remember, an average increases uniformly if the same amount is added to each member of the group.