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.
1.923 * 10 ^ -35 is the answer I got, however you did not specify any formatting to the question, so others may get a completely different answer
2( coin faces) 8( number of times)
Kulay, there is no such thing as a "step by step answer" here. You seem to want a "step by step solution."
I must assume that by 4/5 you actually meant (4/5) and that by 2/3 you meant (2/3). Then your equation becomes:
(4/5)w - 12 = (2/3)w.
The LCD here is 5*3, or 15, so mult. every term by 15:
12w - 180 = 10w.
Add 180 to both sides, obtaining 12 w - 180 + 180 = 10w + 180.
Then 12w = 10w + 180. Simplifying, 2w = 180. What is w?
