ng, in
-A radioactive isotope

\mathrm { X }

is a by-product of nuclear fission with a half-life of

28.7 \mathrm { yr }

. After a nuclear accident, large areas surrounding the site were contaminated with isotope X. If 10 micrograms of

X

is present in a sample, the function

A ( t ) = 10 \left( \frac { 1 } { 2 } \right) ^ { t / 28.7 }

gives the amount

A ( t )

, in micrograms, present after

t

years. Evaluate the function for the given values of

t

and interpret the meaning in context.
a.

A ( 57.4 ) \quad

A ( 100 )

A) a. After

57.4

years the amount of isotope

X

2.5 \mu \mathrm { g }

.
b. After 100 years the amount of isotope

X

is approximately

1.138 \mu \mathrm { g }

.
B) a. After

57.4

years the amount of isotope

X

5 \mu \mathrm { g }

.
b. After 100 years the amount of isotope

X

is approximately

1.138 \mu \mathrm { g }

.
C) a. After

57.4

years the amount of isotope

X

5 \mu \mathrm { g }

.
b. After 100 years the amount of isotope

X

is approximately

0.894 \mu \mathrm { g }

.
D) a. After

57.4

years the amount of isotope

X

2.5 \mu \mathrm { g }

.
b. After 100 years the amount of isotope

\mathrm { X }

is approximately

0.894 \mu \mathrm { g }

Write the Word or Phrase That Best Completes Each Statement eee

Short Answer