Answer:
140.37 in²
Step-by-step explanation:
C = 2πr
42 = 2πr
21 = πr
r = 21/π
A = πr²
A = π × (21/π)²
≈ 140.37 in²
Answer:
18 minutes
Step-by-step explanation:
A = A₀ (½)^(t / T)
where A is the final amount,
A₀ is the initial amount,
t is the time,
and T is the half life.
A = 140 when t = 10. Solve for the half life:
140 = 700 (½)^(10 / T)
0.2 = ½^(10 / T)
log 0.2 = (10 / T) log 0.5
10 / T = 2.32
T = 4.31
When A = 40, t is:
40 = 700 (½)^(t / 4.31)
0.057 = ½^(t / 4.31)
log 0.057 = (t / 4.31) log 0.5
t / 4.31 = 4.13
t = 17.8
Rounded to the nearest whole number, it takes 18 minutes.
Answer:
it's true! it's easier to solve for y because there's no coefficient in front of it unlike the second one that has "9y."
24 = 24 cents. 62 nickels= multiply that by 5. 55 dimes= multiply that by 10. 16 quarters= multiply that by 25. 19 x 50 add together all solutions.
