1.7 Simple & Compound Interest, Growth & Decay

The population of a town decreases exponentially at a rate of 1.7% per year.
The population now is 250 000.
Calculate the population at the end of 5 years.

Give your answer correct to the nearest hundred.

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 .

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

Jan invests $800 at a rate of 3% per year simple interest.
 
Calculate the value of her investment at the end of 4 years.
 

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

There are 30 000 lions in Africa.
The number of lions in Africa decreases exponentially by 2% each year.

Find the number of lions in Africa after 6 years.
Give your answer correct to the nearest hundred.

Newton has a population of 23 000.
The population decreases exponentially at a rate of 1.4% per year.

Calculate the population of Newton after 5 years.

Toby invested £7500 for 2 years in a savings account.
He was paid 4% per annum compound interest.

How much money did Toby have in his savings account at the end of 2 years?

Liam invests £6200 for 3 years in a savings account.
He gets 2.5% per annum compound interest.

How much money will Liam have in his savings account at the end of 3 years?

Katy invests £200 000 in a savings account for 4 years.
The account pays compound interest at a rate of 1.5 % per annum.

Calculate the total amount of interest Katy will get at the end of 4 years.

Naoby invests £6000 for 5 years.
The investment gets compound interest of x% per annum.

At the end of 5 years the investment is worth £8029.35

Work out the value of x.

Jean invests £12000 in an account paying compound interest for 2 years.

In the first year the rate of interest is %
At the end of the first year the value of Jean's investment is £12336

In the second year the rate of interest is %

What is the value of Jean's investment at the end of 2 years?

Jack bought a new boat for £12 500

The value, £V, of Jack's boat at the end of n years is given by the formula

At the end of how many years was the value of Jack's boat first less than 50% of the value of the boat when it was new?

A savings account pays interest at a rate of R% per year.
Jack invests £5500 in the account for one year.

At the end of the year, Jack pays tax on the interest at a rate of 40%.
After paying tax, he gets £79.20

Work out the value of R.

Katy invests £2000 in a savings account for 3 years.

The account pays compound interest at an annual rate of

2.5% for the first year

x% for the second year

x% for the third year

There is a total amount of £2124.46 in the savings account at the end of 3 years.

Work out the rate of interest in the second year.

Katy goes to work by train.

The cost of her weekly train ticket increases by 12.5% to £225

Work out the cost of her weekly train ticket before this increase.