The "k" value should have units and should be negative.
k = -.07 / seconds
Half-Life = ln (.5) / k
Half-Life = ln (.5) / -.07
Half-Life = -.693147 / -.07
Half-Life = 9.9 seconds
(actually, wkpedia says half-life of Krypton 91 is 8.57 seconds)
elapsed time = half-life * log (bgng amt / end amt) / log (2)
elapsed time = 9.9 * log (100 / 10) / 0.30102999566
elapsed time = 9.9 * 1 / 0.30102999566
<span><span>elapsed time = 9.9 * 3.3219280949
</span>
</span><span><span><span>elapsed time = 32.8870881395
</span>
</span>
</span>
<span>elapsed time = 32.89 seconds (rounded)
Source:
http://www.1728.org/halflife.htm
</span>
Well let’s make it a decimal.
.75 = .84 + Y
So if .84 is more than .75 then subtract
.75 from .84 and you have your answer then convert to fraction
Answer:
the greatest common factor is 6
Let's solve for x first,
3x + 5y - 5y = 1 - 5y
3x/3 = 1/3 - 5y/3
x = 1/3 - 5/3y
Let's now plug that into the other equation,
7(1/3 - 5/3y) + 4y = -13
7/3 - 35/3y + 4y = -13
7/3 - 7 2/3y - 7/3 = -13 - 7/3
- 7 2/3y (-3/23) = -15 1/3 (-3/23)
y = 2
The answer is 2
