21 is 42% of 50 , So the correct answer is 50
C. The three angles on the bottom are all exactly the same.
Answer:
0.1037
Step-by-step explanation:
(6C4 × 12C3)/18C7
3300/31824
275/2652 = 0.1037
Answer: 4 years
Step-by-step explanation:
A(0) has to be amount at start. Assume that's 5mg
Then A(t) = 5×(0.5)^(0.25t) = 5×2^(-t/4),
(also known as 5 exp(-λ t) with λ = ln(2)/4, incidentally).
We need to such that A(t) = 2.5mg, or 2^(-t/4) is 1/2, which happens when -t/4 is -1, or t is 4.
