A(r) is a function that gives the area of a circle with radius r. it can be written in equation form as a(r) = 3.14r2. what is the value of a(4)? a. 157.75 b. 25.12 c. 19.14 d. 50.24

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)