Half-life and time with logs Quiz
10 questions · easy to harder · Algebra 2 · score and step-by-step answers
How it works
- 10 questions, about 20 minutes (a timer counts down; you can hide it). Solve it right here: no sign-up.
- 3 questions have choices. For the others you type the answer: a number like 4, −2, 7/2 or 3.5, or for example x = 4, x = 2 or x = −3, (3, 5), 2x + 1. Use ^ for powers (x^2) and sqrt for √. Any form with the same value counts (7/2 = 3.5).
- One question at a time: Back, Next, Mark for review and the question list at the bottom. A calculator is on the screen.
- At the end: your percent and grade, every question right or wrong, why a wrong choice is wrong, and its step-by-step solution. Then practise the lesson with new questions.
Your answers and results are kept in this browser only, so you can close the page and come back.
1 Question 1
A substance has a half-life of 5 years. How much of 80 g is left after 20 years?Type the answer.
2 Question 2
A substance has a half-life of 10 years. How much of 200 mg is left after 30 years?Type the answer.
3 Question 3
A substance has a half-life of 5 years. How long until 80 g decays to 10 g?- A) t = 1080
- B) t = 3
- C) t = 10
- D) t = 15
4 Question 4
A substance has a half-life of 6 hours. How long until 40 mg decays to 5 mg?Type the answer.
5 Question 5
A substance has a half-life of 5 years. How much of 80 g is left after 12 years?Type the answer.
6 Question 6
$500 grows by 4% a year. How many years until it is $800?Type the answer.
7 Question 7
How long until $1000 invested at 6% compounded monthly grows to $2000?- A) t ≈ 2
- B) t ≈ 11.58
- C) t ≈ 1.005
- D) t ≈ 2000
8 Question 8
$2000 grows by 3% a year. How many years until it is $2600?Type the answer.
9 Question 9
$1500 is invested at 6% compounded continuously. How long until it triples?- A) t ≈ 3
- B) t ≈ 4500
- C) t ≈ 18.31
- D) t ≈ 183.1
10 Question 10
How long until $3000 invested at 5% compounded monthly grows to $4500?Type the answer.