Simple Interest Lesson ppt download - Free Printable

You're looking at a set of guided practice problems on Simple Interest. The key formula used throughout is:

> I = Prt

Where:
- I = Interest earned or paid
- P = Principal (the initial amount of money)
- r = Annual interest rate (as a decimal)
- t = Time in years

Let’s go through each problem and explain the solution clearly.

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Problem 5:

> You borrow $57 from a bank at a simple interest rate of 9% per year. How much interest will you pay in one year?

Solution:
- P = $57
- r = 9% = 0.09
- t = 1 year

I = Prt = 57 × 0.09 × 1 = $5.13

✔ Answer: $5.13

*Explanation:* You pay 9% of $57 for one year, which equals $5.13 in interest.

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Problem 6:

> You deposit $354 in a savings account that pays a simple interest rate of 2.5% a year. How much interest will you get over 7 years?

Solution:
- P = $354
- r = 2.5% = 0.025
- t = 7 years

I = Prt = 354 × 0.025 × 7 = $61.95

✔ Answer: $61.95

*Explanation:* Over 7 years, you earn 2.5% per year on $354. Multiply principal × rate × time to get total interest.

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Problem 7:

> You deposit $190 in a savings account that pays a simple interest rate of 4% a year. How much will be in your account after 4 years?

Solution:
First, find the interest earned:
- P = $190
- r = 4% = 0.04
- t = 4 years

I = Prt = 190 × 0.04 × 4 = $30.40

Then, add interest to principal to get total amount:

Total = P + I = 190 + 30.40 = $220.40

✔ Answer: $220.40

*Explanation:* Simple interest doesn’t compound — you only earn interest on the original $190. After 4 years, you have your original money plus $30.40 in interest.

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Problem 8:

> You put $520 in a savings account with a simple interest rate of 6% a year. You take it out after 6 months. How much interest will you get?

Solution:
- P = $520
- r = 6% = 0.06
- t = 6 months = 0.5 years (since interest rate is annual, time must be in years)

I = Prt = 520 × 0.06 × 0.5 = $15.60

✔ Answer: $15.60

*Explanation:* Since 6 months is half a year, we use t = 0.5. You earn half of one year’s interest on $520 at 6%.

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## ✔ Summary of Key Concepts:
- Always convert percent to decimal (e.g., 9% → 0.09).
- Always express time in years (6 months = 0.5 years, 18 months = 1.5 years).
- Simple interest is calculated only on the original principal, not on previously earned interest.
- To find total amount after interest, use: A = P + I

These problems are excellent for practicing the foundational concept of simple interest — essential before moving to compound interest!

Let me know if you’d like to try similar problems or need help with compound interest next!