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SAT Math Practice Question #21344 - SATify | SATify

#21344

exponential

applications

medium

90 sec

Calculator OK

A radioactive substance initially has a mass of $1, 500$ grams. Its mass halves every $20$ years. Which equation represents the mass of the substance $S (t)$ , in grams, $t$ years later?

A.

$S (t) = 1500 (2)^{\frac{t}{20}}$

B.

$S (t) = 1500 (\frac{1}{2})^{20 t}$

C.

$S (t) = 1500 (\frac{1}{2})^{\frac{t}{20}}$

D.

$S (t) = 1500 (\frac{1}{2})^{\frac{20}{t}}$