Simple & Compound Interest, Growth & Decay Practice Questions

Daniel invests £3200 in a savings account for 5 years.

The account pays simple interest at a rate of 4% per year.

Work out the total amount in Daniel's account at the end of 5 years.

The Elm Building Society pays simple interest at a rate of 1.5% per year.

Work out the total interest Naomi would earn in 4 years with the Elm Building Society.

The Oakfield Bank pays compound interest at a rate of 1.5% per year.

Work out how much more interest Naomi would earn in 4 years with the Oakfield Bank than with the Elm Building Society.

Hannah buys a new delivery van for £24 500.

The value of the van depreciates by 18% in the first year.
It then depreciates by 12% in each following year.

Work out the value of the van at the end of 4 years.
Give your answer correct to the nearest £100.

Femi wants to invest £14 000 for 4 years.

He sees these two accounts.

Account	Interest
Harbour Savings	Compound interest 3.1% for each year
Riverside Savings	Compound interest 5.5% for the first year, then 2.2% for each extra year

Which account will give Femi the most interest at the end of 4 years?
You must show all your working.

In 2015 a flat was worth £185 000.

In 2022 the same flat was worth £238 000.

Over these 7 years the value of the flat increased by $x\%$ each year.

Work out the value of $x$.
Give your answer correct to 2 significant figures.

Write down an expression, in terms of $n$, for the value in pounds of Leah's investment at the end of $n$ years.

Work out the value of Leah's investment at the end of 6 years.
Give your answer correct to the nearest penny.

Work out the total interest earned in the 6 years as a percentage of the £6500 she invested.
Give your answer correct to 1 decimal place.

Complete the iterative formula.

$F_{n+1} = \ldots\ldots\ldots$

Work out the number of fish in the lake at the end of 3 years.
Give your answer correct to the nearest whole number.

Write down what the number 0.85 tells you about the amount of the drug in the patient's bloodstream.

Work out the amount of the drug in the patient's bloodstream 6 hours after the dose is given.
Give your answer correct to 3 significant figures.

The patient may be given a second dose only when the amount of the drug in the bloodstream is less than 50 mg.

Work out the least whole number of hours after the first dose that the patient may be given a second dose.

Work out the percentage by which the value of the car depreciated each year.
Give your answer correct to 1 decimal place.

The value of the car continues to depreciate by this same percentage each year.

Work out the number of complete years, from new, after which the value of the car is first less than £5000.

Work out how much money is in the account at the end of 3 years, after Sonia has made her third withdrawal.

Sonia says,

"Because interest is added every year, the amount in my account will never fall below £15 000."

Is Sonia correct?
You must give a reason for your answer.