<span>4(r+1.9)-9r=12.2
</span><span>4r + 7.6 -9r = 12.2
-5r = 12.2 - 7.6
-5r = 4.6
r = 4.6/-5
r = - 0.92</span>
Answer:
c. 22/24
Step-by-step explanation:
perimeter = 3/8 + 3/8 + 1/6
perimeter = 22/24 or 11/12
<span>2y = x + 3 then x = 2y - 3
5y = x - 7 then x = 5y + 7
so
</span>2y - 3 = 5y + 7
2y - 5y = 7 + 3
-3y = 10
y = -10/3
y = -3 1/3
<span>2y = x + 3
</span>2 (-10/3) = x + 3
-20/3 - 3 =x
-29/3 = x
-9 2/3 =x
or
x = -9 2/3
solutions: x = -9 2/3 and y = -3 1/3
After 1 hour, 360 g decays to 180 g.
After another hour (total 2 hours), 180 g decays to 90 g.
After another hour (total 3), 90 g decays to 45 g.
After one more (total 4), 45 g decays to 22.5 g.
More quickly, with a half-life of 1 hour, the 360 g of starting material decays to
(360 g) / 2⁴ = 22.5 g
In general, if the half-life is 1 hour, then after <em>n</em> hours, an initial amount <em>A</em> of this substance decays according to
<em>A</em> / 2<em>ⁿ</em>
