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An original sample of K-40 has a mass of 25.00 grams. After 3.9 × 109 years, 3.125 grams of the original sample remains unchanged. What
is the half-life of K-40?
(1) 1.3 × 109 y (3) 3.9 × 109 y
(2) 2.6 × 109 y (4) 1.2 × 1010 y

Respuesta :

Since3122015
[tex]\frac{25}{3.125}=8=2^3\\\\\frac{3.9*10^9}{3}\\1.3*10^9[/tex]

(1) 1.3*10^9 years

Answer:

La respuesta correcta es [tex]1.3*10^{9}[/tex]

Explanation:

Hello! Let's solve this!

First we have to know the mass / mass exponent without changes

The data is:

m = 25 g

mc (mass without changes) = 3.125g

25 / 3,125 = 8 = [tex]2^{3}[/tex]

The exponent is 3, so we divide the number of years by three.

[tex]\frac{3.9*10^{9} }{3}[/tex]

La respuesta correcta es [tex]1.3*10^{9}[/tex]