Answer: t½ = 7.80
Explanation:
This question is lacking the (b) part and source similar online are not the same since some values has been altered. However I'll answer the one present here.
Nt = No.e^-yt
Note : y is used to represent the greek alphabet lambda
Nt = 91.5
No = 100
t = 1 year
Nt = No. e^-yt
91.5 = 100e^-yt
e^-y = 91.5/100
Take ln on both sides
In (e^y) = ln(100/91.5)
y = ln(1.0929)
y = 0.0888
t½ = 0.693 / y
t½ = 0.693 / 0.0888
t½ = 7.80
