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:
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Answer:
Terminating decimals have a finite number of digits after the decimal point. Repeating decimals have one or more repeating numbers or sequences of numbers after the decimal point, which continue infinitely.
Answer:
An even number
Step-by-step explanation:
Integers which are multiples of 2, are even numbers.
Integers which aren't multiples of 2, are odd numbers.
As integers can be positive and negative both, odd and even numbers also can be positive and negative.
Answer:
A(1,6)
Step-by-step explanation:
SOOO, we're gonna graph it okay?
I graphed it, and A was the only one on the line.
I hope this helps