2007-01-30 08:20:22 · 6 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
.03125 is the percentage as a decimal. As a fraction it's 3125/100000
625/20000
125/4000
25/800
5/160
1/32
1/2^5
half life = - log (1/2)
- log (1/2^5) = - (-5) = 5
So 5 half-lives are required.
Multiply the 10 minutes by 5 to get 50 minutes.
2007-01-30 08:32:13 · answer #1 · answered by bequalming 5 · 0⤊ 0⤋
Well, first you want to find out how many N 3.125% is. Once you have that number, you need to see how long it would take for 13N to get down that far, based on the knowledge that the half-life is ten minutes (every ten minutes, half of 13N remains; how long will it take to get down to the 3.125% amnt.). I will not tell you the answers to YOUR homework, because if you don't learn anything, you'll wind up burger-flipping at McDonald's.
2007-01-30 16:27:57 · answer #2 · answered by gilgamesh 6 · 0⤊ 0⤋
Every 10 minutes, the amount is reduced by half. In x minutes, there will be 1/2^(x/10) of the original amount left. Put into equation form:
1/2^(x/10)=.03125
If you put .03125 into fraction form, you'll see that it equals 1/32. Therefore...
1/2^(x/10)=1/32
2^(x/10)=2^5
x/10=5
x=50
It will take 50 minutes.
2007-01-30 16:29:47 · answer #3 · answered by Chris S 5 · 0⤊ 0⤋
50 minutes
2007-01-30 16:26:16 · answer #4 · answered by Anonymous · 0⤊ 0⤋
50% in 10 min.
25% in 20 min.
12.5% in 30 min.
6.25% in 40 min.
3.125% in 50 min.
2007-01-30 16:27:40 · answer #5 · answered by Johann Flargnik 3 · 0⤊ 0⤋
half-life = ln(2)/constant
10 minutes = 0.693/constant
.06944 = constant
For exponential decay:
N(t)= N(0) * e ^[-0.06944 * t]
0.03125 = 1 * e^[-0.06944 * t]
Take the natural log of both sides:
-3.4657 = -0.06944 * t
50 minutes = t
Done.
2007-01-30 17:02:12 · answer #6 · answered by Jerry P 6 · 0⤊ 0⤋