100%-20%=80%
25×80%=20. As a result, Kyle pays $20 for the shirt. Hope it help!
Answer:
25
Step-by-step explanation:
We know that the standard error of the sampling distribution of sample means is
Standard error=standard deviation/√n
√n=standard deviation/Standard error
n=(standard deviation/Standard error)²
We are given that standard deviation=5 and standard error=1. So,
n=(5/1)²
n=5²
n=25.
Thus, the required sample size is 25.
A geologist in South America discovers a bird skeleton that contains 80% of its original amount of C-14
We use formula
N0= initial amont of C-14 (at time t=0)
N= amount of C-14 at time t
t= time, in years
k= 0.0001
N is 80% of N0 that is
Divide both sides by N_o
Take ln on both sides
ln(0.8) = -0.0001t ln(e)
ln(0.8) = -0.0001t
Divide both sides by -0.001
t = 2231.435513
The age of the bird skeleton is 2231 years old