Answer:
9-(-15)
Step-by-step explanation:
because it would be changed to 9+15
Answer:
D. a matched pairs experiment.
Step-by-step explanation:
A matched pairs experiment can be designed when there are only two possible treatment conditions (Screen A and Screen B) within an experiment and the subjects can be accordingly grouped into pairs (Both sides of the body of a same person, since both sides present the same skin complexion). Within each pair (both sides of the subject's body), subjects are randomly assigned (coin toss) to different treatments.
Therefore, this experiment is an example of a matched pairs experiment.
For part (a) the answer is 400 grams for part (b) 198.63 grams and for part (c) 20 years.
<h3>What is exponential decay?</h3>
During exponential decay, a quantity falls slowly at first before rapidly decreasing. The exponential decay formula is used to calculate population decline and can also be used to calculate half-life.
We have an equation for radioactive decay:

a) Plug t = 0

m(0) = 400 grams
b) plug t = 20 years

After solving:
m(20) = 198.63 grams
c) Plug m(t) = m(0)/2 = 400/2 = 200 grams

x = 19.80 years ≈ 20 years
Thus, for part (a) the answer is 400 grams for part (b) 198.63 grams and for part (c) 20 years.
Learn more about the exponential decay here:
brainly.com/question/14355665
#SPJ1
Answer:
A. 31 cm
Step-by-step explanation:
Hopefully its right :)