the life of plutonium-239 is 24,300 years. if a nuclear bomb released 8kg of this isotope, how many years would pass before the amount is reduced to 1 kg.

97200yrs,

Explanation:

Given parameters:

Half-life of Plutonium - 239  = 24300yrs

Mass of the isotope  = 8kg

Unknown:

Number of years it will take for the amount to reduce to 1kg = ?

Solution:

The half -life of any substance is the time taken for half of the compound to decay to half its original composition.

               Start     first half life     second half life   third half life

mass       8kg              4kg                   2kg                    1kg

Time         0yrs            24300            48600               97200

By 97200yrs, the mass would have been 1kg

its first and third is your answer i did the qustion the fourth isnt right