NBT NBT Mathematics: Finance, Growth and Decay 2

Question 1

What is the total amount after investing $2,000 at 5% simple interest per year for 3 years?

Accepted Answer

$2,300

Answer

Simple interest = 2000 × 0.05 × 3 = $300, so the total is $2,300.

Question 2

$1,000 is invested at 10% per year compounded annually. What is the value after 2 years?

Accepted Answer

$1,210

Answer

A = 1000(1.10)^2 = $1,210.

Question 3

A car worth $20,000 depreciates at 15% per year on the reducing balance. What is it worth after 2 years?

Accepted Answer

$14,450

Answer

A = 20000(0.85)^2 = $14,450.

Question 4

A town of 5,000 people grows by 4% each year. Which expression gives the population after n years?

Accepted Answer

5000(1.04)^n

Answer

Growth of 4% per year means multiplying by 1.04 each year.

Question 5

A radioactive sample of 80 g has a half-life of 8 days. How much remains after 24 days?

Accepted Answer

10 g

Answer

24 days is 3 half-lives, so 80 × (1/2)^3 = 10 g.

(NBT) National Benchmark Test Practice Test