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.
Answer:
<h2><em><u>-x</u></em><em><u> </u></em><em><u>=</u></em><em><u> </u></em><em><u>2</u></em></h2>
Step-by-step explanation:
<em><u>If</u></em><em><u>,</u></em>
x = -2
<em><u>Then</u></em><em><u>,</u></em>
-x = -(-2)
=> <em><u>-x = 2 (Ans)</u></em>
18 - 7x = -20.5
Subtract 18 from each side:
-7x = -38.5
Divide both sides by -7:
x = -38.5 / -7
x = -5.5 = 5 1/2
The answer is D.
You set (x+15) equal to 40 and solve for x.
x+15=40
-15 -15
x=25
Hope this helps!
Answer:
3850m^2
Step-by-step explanation:
hope this helps
