This could be rephrased as:
You start with 100 grams of a substance. One year later you have 70 grams. What is the half-life?
We need this formula:
half-life = (time * natural log (2)) / natural log (beginning amount / ending amt)
half-life = (1 year * .69315) / natural log (100 / 70)
half-life = (.69315) / 0.35667494396
half-life = 1.9433661145 years
Rounding to nearest year half-life = 2 years
Sourse: https://www.1728.org/halflif2.htm
(See problem 3)
The answer is B. 53/20 !!!!
Answer:
19.193 million
Step-by-step explanation:
Put the given value in the formula and do the arithmetic.
P(220) = 19.71/(1 +61.22e^(-0.03513·220))
P(220) = 19.71/(1 +61.22e^-7.7286) = 19.71/(1 +0.02694046)
P(220) ≈ 19.193 . . . million
Answer:
We need a sample of at least 752 students.
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of
, and a confidence level of
, we have the following confidence interval of proportions.

In which
z is the zscore that has a pvalue of
.
The margin of error of the interval is:

90% confidence level
So
, z is the value of Z that has a pvalue of
, so
.
How large of a sample must she have to get a margin of error less than 0.03
We need a sample of at least n students.
n is found when M = 0.03.
We have no information about the true proportion, so we use
.






Rounding up
We need a sample of at least 752 students.