Question 1191816: An isotope of stornium, Sr90 has a half life of 25 years. Find the mass of Sr90 remaining from a sample of 22 mg after 150 years Found 3 solutions by ikleyn, math_tutor2020, josgarithmetic:Answer by ikleyn(52879) (Show Source):
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An isotope of stornium, Sr90 has a half life of 25 years. Find the mass of Sr90 remaining from a sample of 22 mg after 150 years
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You can put this solution on YOUR website!
A slightly informal approach:
The half-life is 25 years. Since 150 years elapse, this is 150/25 = 6 half-life periods.
The original mass (22) is cut in half exactly 6 times.
(1/2)^6 = (1^6)/(2^6) = 1/64
The starting mass is multiplied by 1/64
22*(1/64) = 0.34375
A more formulaic approach:
y = a*(0.5)^(x/H)
y = 22*(0.5)^(x/25)
y = 22*(0.5)^(150/25)
y = 22*(0.5)^6
y = 0.34375
We have a = 22 as the starting amount and H = 25 as the half-life. Plugging in x = 150 years leads to a resulting leftover mass of y = 0.34375 mg
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