The half-life of a certain isotope is 15 minutes. how much of a 400 g sample will remain after 90 minutes? 12.5 g6.25 g26.7 g66.7 g25 g

There is a total of 6 half lives that need to take place.

ONE HALF LIFE = 200

TWO HALF LIFES = 100

THREE HALF LIFES  = 50

FOUR HALF LIFES = 25

FIVE HALF LIFES = 12.5

SIX HALF LIFES = 6.25

The answer is 6.25g

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