Simple & Compound Interest, Growth & Decay (OCR GCSE Maths: Foundation): Exam Questions

Lukas invests £350 in a savings account.
At the end of 4 years he has received a total of £53.20 simple interest.

Work out the annual rate of simple interest.

Maya invests some money in a savings account that pays 4% simple interest per year.

After 3 years, Maya has earned £36 in interest.

Find how much money Maya invested.

A city has a population of 215 000 people.

The population of the city increases by 1.5% each year.

What is the population of the city after 3 years?

The value of a new TV is £850.
The value of the TV depreciates by 12% each year.

Work out the value of the TV after 2 years.

Trina invests $16000 at a rate of 5% per year compound interest.

Work out the value of her investment at the end of 4 years.

$.........................

Gino invests $6000 for 5 years at a rate of 1.2% per year compound interest.

Calculate the value of his investment at the end of the 5 years. Give your answer correct to the nearest dollar.

$ .................................................

Lucia invests $5000 at a rate of 4.5% per year compound interest.

Calculate the value of her investment at the end of 7 years.

$ .................................................. 

Ella invests $4000 for 3 years at a rate of 1.2% per year compound interest.

Calculate the value of her investment at the end of the 3 years.

$...................................................

Javier invests $750 for 3 years at a rate of 1.8% per year compound interest.

Calculate the value of his investment at the end of the 3 years.

$ ................................................... 

Hawa invests $750 at a rate of 3.5% per year compound interest.

Calculate the value of his investment at the end of 3 years.

$ .............................. 

A scientist is studying a population of yeast cells in a culture dish.

At the start (time days), there are 800 yeast cells.

The number of yeast cells increases by 5% every day.

Complete the table to show the number of yeast cells in the dish each day.

Round each value to the nearest whole number.

On the grid below, plot the points from your completed table.

The dish can support a maximum of 1000 yeast cells.

After day 4, the number of yeast cells continues to grow but eventually levels off at 1000.

Describe how the shape of the graph would change after day 4.

Sarah invests £16 000 in a savings account.
She gets 2.5% compound interest per annum.

After years Sarah has £17 230.25

Work out .

Two samples of bacteria are prepared in a laboratory.

Sample A contains 100 bacteria.
The number of bacteria in the sample increase by 60% each hour.

Sample B contains 3000 bacteria.
The number of bacteria in the sample decreases at a rate of 19% per hour.

After 5 hours, which sample contains more bacteria.
You must show all your working.

Heather wants to invest £35 000 in a bank for 4 years.

Bank A  offers 3% compound interest.

Bank B offers 5.1% interest for the first year and 2.5% compound interest for the remaining 3 years.

Which bank will give Heather the most interest at the end of the 4 years.
You must show all your working.

$12000 is invested at a rate of n% per year simple interest.
At the end of 3 years the value of the investment is $12900.

Find the value of .

= ................................. 

Sonia wants to invest $5000 for 6 years.

Bank A pays compound interest at a rate of 3.5% per year.
Bank B increases the $5000 by 22% at the end of 6 years.

Which bank will give Sonia the most money at the end of 6 years and by how much?
You must show all your working.

Riya invests $30000 at a rate of 2.5% per year compound interest.

Calculate the value of her investment at the end of 7 years.
Give your answer correct to the nearest dollar.

$ ................................................. 

Six years ago a farmer invested $3750 at a rate of 4% per year compound interest.

i) Calculate the total value of his investment after the 6 years. Give your answer correct to the nearest dollar.

$ ............................................... [3]

ii) The farmer wants to spend his investment on buying goats. Goats cost $126 each.

Work out the maximum number of goats he can buy and the amount of money left over.

Number of goats ..............................................
Amount of money left over $
............................................... [4]

The farmer grows carrots.
In 2018 the selling price for carrots was $96 per tonne.
In 2019 this selling price increased by 18%.

Work out the increase in the selling price from 2018 to 2019.

$ ..............................................

Paula invests $600 at a rate of% per year simple interest.
At the end of 10 years, the total interest earned is $90.

Find the value of

=........................................

$8400 is invested for 2 years at a rate of 3.5% per year compound interest.
Work out the total amount of interest earned by the end of the 2 years.

$.................................................... 

Harry invests $800 for 2 years at a rate of 3% per year compound interest.

Calculate the amount of interest he receives at the end of the 2 years.

$ ...........................

Tomas borrows $5000 for 3 years at a rate of 2.5% per year compound interest.
He pays back the whole amount, with interest, at the end of 3 years.

Calculate the total amount of money he pays back at the end of the 3 years.

$ ..............................