Answer:
Rate of Decay = 8%
Step-by-step explanation:
The decay formula is:

Where F is the final value (here, it is given as "Y")
P is the initial value (here, given as 20,000)
r is the rate of decay (what we need to find)
t is the time (given as 2)
Comparing both the equations:

We see that:
1 - r =0.92
We solve for "r":
1 - 0.92 = r
0.08 = r
The rate of decay is 0.08, as a percentage, we need to multiply by 100, so we have:
0.08 * 100 = 8%
Rate of Decay = 8%
12:15 does not belong, since that is a ratio of 4:5, whilst the others are all 3:4.
Answer:
2000
Step-by-step explanation:
Hello,
A or C means 2 ways
and then a digit means 10 ways 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
so in total we have 2*10*10*10 = 2000 possible codes
Hope this helps
None of the answers are correct because it would be 4, 10, 12, 17, then 41
The answer she has is not correct.
All the steps she did are correct, except they forgot to convert the decimal answer into the proper percentage by multiplying it by 100.
The correct answer should be 0.125 * 100 = 12.5%