Answer: 693 years
Step-by-step explanation:
Expression for rate law for first order kinetics is given by:

k = rate constant
t = time taken for decomposition = 1
= Initial amount of the reactant
= amount of the reactant left =



for half life : 

Putting in the values , we get


Thus half life of this isotope, to the nearest year is 693.
Answer:
The cellphone towers height is 1020 ft.
Step-by-step explanation:
This question is solved using proportions, by a rule of three.
A 10-ft post casts a 14-inch shadow.
Each feet has 12 inches, which means that a post with 10 feet will cast a 14/12 = 1.167 ft shadow. How tall is the cell-phone tower with a 119-feet shadow?
10 feet post - 1.167 ft shadow
x feet tower - 119 feet shadow
Applying cross multiplication:



The cellphone towers height is 1020 ft.
Answer:
Our decision rule will be to reject The null hypothesis H0 if the test statistic is less than -1.645, or if it is greater than +1.645.
Step-by-step explanation:
The hypotheses would be;
Null hypothesis;H0: μ = 500
Alternative hypothesis;Ha: μ ≠ 500
Since it's two - tailed at 0.1 level of significance, then each tail will contain 5% or 0.05. From the z-table attached, the corresponding critical value of 0.05 is approximately 1.645 standard deviations from the mean.
Thus, our decision rule will be to reject The null hypothesis H0 if the test statistic is less than -1.645, or if it is greater than +1.645.