Answer:
1.) 8.09g ; 2) 206.7 years
Step-by-step explanation:
Given the following :
Half-life(t1/2) of Uranium-232 = 68.9 years
a) If you have a 100 gram sample, how much would be left after 250 years?
Initial quantity (No) = 100g
Time elapsed (t) = 250 years
Find the quantity of substance remaining (N(t))
Recall :
N(t) = No(0.5)^(t/t1/2)
N(250) = 100(0.5)^(250/68.9)
N(250) = 100(0.5)^3.6284470
N(250) = 100 × 0.0808590
= 8.0859045
= 8.09g
2) If you have a 100 gram sample, how long would it take for there to be 12.5 grams remaining?
Using the relation :
N / No = (1/2)^n
Where N = Amount of remaining or left
No = Original quantity
n = number of half-lifes
N = 12.5g ; No = 100g
12.5 / 100 = (1/2)^n
0.125 = (1/2)^n
Converting 0.125 to fraction
(1/8) = 1/2^n
8 = 2^n
2^3 = 2^n
n = 3
Recall ;
Number of half life's (n) = t / t1/2
t = time elapsed ; t1/2 = half life
3 = t / 68.9
t = 3 × 68.9
t = 206.7 years
Answer:
7.4 seconds
Step-by-step explanation:
878 = 16 t^2 divide both sides of the equation by 16
54.875 = t^2 take positive sq rt
7.4 seconds
Answer:
per year: $47,760 per year
per week: $918.46 per week
Step-by-step explanation:
$3980 per month x 12 months = $47,760 per year
$47,760 per year divided by 52 weeks = $918.4615384615
Since we're talking money, let's round off our answer to the hundredths place ($918.46 per week)
Double check our answer (918.46 x 52 = 47,760) great!