Question

Polonium-218 has a half-life of about 3 minutes.

After 15 minutes, how many milligrams of a 120 mg sample will remain?

A. 1.875 mg
B. 3.75 mg
C. 4.8 mg
D. 7.5 mg

Answer 1

the answer will be c.4.8 mg 

Answer 2

Option B - 3.75 mg

Explanation:

Given : Polonium-218 has a half-life of about 3 minutes.

To find : After 15 minutes, how many milligrams of a 120 mg sample will remain?

Solution :

Considering an exponential model,

`y=a_0(x)^(t)/(n)`

Where, y is the total amount

`a_0` is the original amount
`a_0=120`

x is the half-life of Polonium-218
`x=(1)/(2)=0.5`

t is the time taken t=15 minutes

n is the time spent n=3 minutes

Substitute the values in the exponential model,

`y=120(0.5)^{(15)/(3)}`

`y=120(0.5)^5`

`y=120(0.03125)`

`y=3.75`

Therefore, Option B is correct.

3.75 mg is required amount.