Answer
Half life = 4.6 days
Explanation
The amount of a material left is given as
N = N₀ e⁻ᵏᵗ
Where
Half-life is the time it takes a substance to reach half of its original value.
N₀ = Initial mass (at time t = 0) = 45 grams
N = mass at time = (45/2) = 22.5 grams
k = a positive constant that depends on the substance itself and on the units
used to measure time = 0.15 /day
t = time, in days = ?
N = N₀ e⁻ᵏᵗ
22.5 = 45 e⁻⁰.¹⁵ᵗ
Divide both sides by 45
(22.5/45) = e⁻⁰.¹⁵ᵗ
e⁻⁰.¹⁵ᵗ = 0.50
Take the natural logarithms of both sides
In e⁻⁰.¹⁵ᵗ = In 0.50
-0.15t = -0.693
Divide both sides by -0.15
(-0.15t/-0.15) = (-0.693/-0.15)
t = 4.6 days
Hope this Helps!!!