Advanced MathHardFour half-lives of a sample
Advanced Math practice question
A sample contains 80 milligrams of a substance whose amount halves every 6 hours. How many milligrams remain after 24 hours?
Answer: 5
24 hours is four half-lives: 80 → 40 → 20 → 10 → 5 milligrams.
Common wrong answers
- If you answered 10
- 10 mg is after three half-lives (18 hours); 24 hours is four.
- If you answered 20
- 20 mg is after two half-lives (12 hours).
- If you answered 3.33
- The decay halves repeatedly rather than dividing 80 by 24.
More Advanced Math questions
- Hard
A population of bacteria doubles every 3 hours. If it starts at 500, which function models the population P af… - Hard
How many real solutions does x² + 4x + 5 = 0 have? - Hard
A car worth $20,000 loses 15% of its value each year. What is its value after 2 years? - Hard
An investment of $1,000 grows at 6% per year, compounded annually. Which expression gives its value after t ye… - Hard
If f(x) = x² − 1 and g(x) = x + 2, what is g(f(3))? - Hard
The parabola y = x² − 8x + 12 crosses the x-axis at two points. What is the x-coordinate of the vertex?
Not affiliated with the College Board. SAT is a trademark of the College Board.