Sec 1 Maths · Percentage

Simple interest questions with answers

Practice questions on simple interest, from the basics up to exam level, each with a full worked solution. Try them on paper first, then open the solution to check your working.

Worked example

Ben borrows $12,000 from a bank at 5% per annum simple interest. Find the interest Ben has to pay after 6 years.

Step 1 of 1

Substitute P, R and T into the formula

I = \dfrac{PRT}{100}

I = \dfrac{12000 \times 5 \times 6}{100}

= 3600

The interest is $3600.

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Questions

Question 1Find the interest
Devi deposits $4,000 in a bank that pays simple interest of 2% per annum. Find the interest earned after 5 years.
Show the worked solution
1. Step 1: Substitute P, R and T into the formula $I = \dfrac{PRT}{100}$ $I = \dfrac{4000 \times 2 \times 5}{100}$ $= 400$ The interest is $400.
Question 2Find the total amount
Nur deposits $2,000 in a bank that pays simple interest of 3.5% per annum. Find the total amount in the account after 5 years.
Show the worked solution
1. Step 1: Substitute P, R and T into the formula $I = \dfrac{PRT}{100}$ $I = \dfrac{2000 \times 3.5 \times 5}{100}$ $= 350$
2. Step 2: Total amount = principal + interest $\text{Amount} = 2000 + 350$ $\phantom{\text{Amount}} = 2350$ The total amount is $2350.
Question 3Time in months
Farah borrows $5,000 from a bank at 2% per annum simple interest. Find the interest Farah has to pay after 15 months.
Show the worked solution
1. Step 1: T is in years: change the months to years (÷ 12) $T = \dfrac{15}{12}$ $\phantom{T} = 1.25$
2. Step 2: Substitute P, R and T into the formula $I = \dfrac{PRT}{100}$ $I = \dfrac{5000 \times 2 \times 1.25}{100}$ $= 125$ The interest is $125.
Question 4Find the amount deposited
Chen Wei deposits some money in a bank that pays simple interest of 3% per annum. After 4 years, the interest earned is $288. Find the amount of money Chen Wei deposited.
Show the worked solution
1. Step 1: Put the numbers you know into the formula $I = \dfrac{PRT}{100}$ $288 = \dfrac{P \times 3 \times 4}{100}$
2. Step 2: Find the amount deposited: make P the subject of the formula $P = \dfrac{288 \times 100}{3 \times 4}$ $= 2400$ Chen Wei deposited $2400.
Question 5Find the rate or the time
Nur deposits $1,500 in a bank that pays simple interest of 4% per annum. The interest earned is $360. Find the number of years for which the money was deposited.
Show the worked solution
1. Step 1: Put the numbers you know into the formula $I = \dfrac{PRT}{100}$ $360 = \dfrac{1500 \times 4 \times T}{100}$
2. Step 2: Find the number of years: make T the subject of the formula $T = \dfrac{360 \times 100}{1500 \times 4}$ $= 6$ The money was deposited for $6$ years.

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Worked example

Ben borrows $12,000 from a bank at 5% per annum simple interest. Find the interest Ben has to pay after 6 years.

Step 1 of 1

Substitute P, R and T into the formula

I = \dfrac{PRT}{100}

I = \dfrac{12000 \times 5 \times 6}{100}

= 3600

The interest is $3600.

Questions

Question 1Find the interest

Devi deposits $4,000 in a bank that pays simple interest of 2% per annum. Find the interest earned after 5 years.

Show the worked solution

Step 1: Substitute P, R and T into the formula $I = \dfrac{PRT}{100}$ $I = \dfrac{4000 \times 2 \times 5}{100}$ $= 400$ The interest is $400.

Question 2Find the total amount

Nur deposits $2,000 in a bank that pays simple interest of 3.5% per annum. Find the total amount in the account after 5 years.

Show the worked solution

Step 1: Substitute P, R and T into the formula $I = \dfrac{PRT}{100}$ $I = \dfrac{2000 \times 3.5 \times 5}{100}$ $= 350$
Step 2: Total amount = principal + interest $\text{Amount} = 2000 + 350$ $\phantom{\text{Amount}} = 2350$ The total amount is $2350.

Question 3Time in months

Farah borrows $5,000 from a bank at 2% per annum simple interest. Find the interest Farah has to pay after 15 months.

Show the worked solution

Step 1: T is in years: change the months to years (÷ 12) $T = \dfrac{15}{12}$ $\phantom{T} = 1.25$
Step 2: Substitute P, R and T into the formula $I = \dfrac{PRT}{100}$ $I = \dfrac{5000 \times 2 \times 1.25}{100}$ $= 125$ The interest is $125.

Question 4Find the amount deposited

Chen Wei deposits some money in a bank that pays simple interest of 3% per annum. After 4 years, the interest earned is $288. Find the amount of money Chen Wei deposited.

Show the worked solution

Step 1: Put the numbers you know into the formula $I = \dfrac{PRT}{100}$ $288 = \dfrac{P \times 3 \times 4}{100}$
Step 2: Find the amount deposited: make P the subject of the formula $P = \dfrac{288 \times 100}{3 \times 4}$ $= 2400$ Chen Wei deposited $2400.

Question 5Find the rate or the time

Nur deposits $1,500 in a bank that pays simple interest of 4% per annum. The interest earned is $360. Find the number of years for which the money was deposited.

Show the worked solution

Step 1: Put the numbers you know into the formula $I = \dfrac{PRT}{100}$ $360 = \dfrac{1500 \times 4 \times T}{100}$
Step 2: Find the number of years: make T the subject of the formula $T = \dfrac{360 \times 100}{1500 \times 4}$ $= 6$ The money was deposited for $6$ years.