Question

element x has a half life of 5,700 years. when 25% of the original element x is still remaining how many years have gone by? 11,400 years 2,850 years 5,700 years 17,100 years

Explanation:

Step1: Understand half - life concept

The half - life of a substance is the time it takes for half of the substance to decay. So, after one half - life (5700 years for Element X), 50% of the original substance remains.

Step2: Determine number of half - lives for 25% remaining

If 50% remains after 1 half - life, then to have 25% remaining, we need another half - life. Because 50% of 50% is 25% (i.e., $\frac{1}{2}\times\frac{1}{2}=\frac{1}{4} = 25\%$). So the number of half - lives passed is 2.

Step3: Calculate total time

Since one half - life is 5700 years, for 2 half - lives, the total time is $5700\times2 = 11400$ years.

Answer:

11,400 years