The formula for calculating simple interest is:

$I = P \times r \times t$

Where:

• $I$ is the interest,
• $P$ is the principal amount (initial deposit),
• $r$ is the interest rate (in decimal form),
• $t$ is the time in years.

For this problem:

• $P = 100$,
• $r = 0.05$ (since 5% = 0.05),
• $t = 1$ year.

Now calculate the interest:

$I = 100 \times 0.05 \times 1 = 5$

Thus, Ciara will earn $5 in interest after 1 year.

The correct answer is B. $5.

Would you like more details on simple interest or another explanation?

Here are 5 related questions to explore further:

1. How is simple interest different from compound interest?
2. How much interest would Ciara earn in 3 years with the same conditions?
3. What would the interest be if the rate were 7% instead of 5%?
4. If Ciara deposits $200 instead of $100, how would the interest change?
5. What formula is used to calculate the total amount in the account after interest?

Tip: Always convert percentages to decimal form before using them in formulas.