The half-life of radium is 1690 years. If 80 grams are present now, how much will be present in 870 years? grams

A(t) = amount remaining in t years

= A0ekt, where A0 is the initial amount and k is a constant to be determined.

Since A(1690) = (1/2)A0 and A0 = 80,

we have 40 = 80e1690k

1/2 = e1690k

ln(1/2) = 1690k

k = -0.0004

So, A(t) = 80e-0.0004t

Therefore, A(430) = 80e-0.0004(430)

= 80e-0.172

≈ 67.4 g

Step-by-step explanation:

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x divided by 8=y

step-by-step explanation:

answer: expected value of x = 1.0

step-by-step explanation:

p(x=0) = 0.25

p(x=1) = 0.50

p(x=2) = 0.25

expected value for x = 0×0.25 + 1×0.5 + 2×0.25 = 1.0