Answer is.. 144.
2 x 4 = 8
9 x 8 = 72
72 x 2 = 144
X-4y=-2
-x. -x
4y=-2-x
4y=x-(-2)
/4. /4
Y=4x+2/4
3x-y=5
-3x. -3x
-y=5-3x
-y=-3x+5
/-1. /-1
Y=3x-5
The general way to work this out is to solve the general expression for
the remaining quantity versus half-life, using logarithms. But that's not
necessary with these numbers.
Look at the numbers:
-- 3 mg is 1/4 of 12 mg.
-- 1/4 is the product of (1/2) x (1/2).
-- So the 3 mg is what's left of 12 mg after 2 half-lives.
The 26 minutes must be two half-lives.
-- The half-life of that substance is 26/2 = <em>13 minutes</em>.
Go Maggie !
Answer:
2nd and 3rd
Step-by-step explanation:
