Question

Plutonium-240 decays according to the function


where Q represents the quantity remaining after t years and k is the decay constant, 0.00011... How long will it take 24 grams of plutonium-240 to decay to 20 grams?

Answer 1

it should be -kt if k is positive (since you want decay)

Answer 2

right , woops :)

Answer 3

$$
\Large \rm {Q = Q_o \cdot e^{-kt}
\\ where ~ Q_o ~ is ~ quantity~at~time~ zero
}

$$

Answer 4

I still don't get it.