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Element X is a radioactive isotope such that every 21 years, its mass decreases by half. Given that the initial mass of a sample of Element X is 40 grams , how much of the element would remain after 9 years , to the nearest whole number?

Respuesta :

MathPhys

Answer:

30 grams

Step-by-step explanation:

Use the half life equation:

A = P (½)^(t / T)

where P is the initial amount, t is time, and T is the half life length.

Given P = 40, t = 9, and T = 21:

A = 40 (½)^(9 / 21)

A ≈ 30