A circular rug has a circumference of 12.56 feet. What is the area of the rug? (Use 3.14 for .) A. 6.28 square feet B. 25.12 squ
are feet C. 56.52 square feet D. 12.56 square feet
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Staals half
1 gram left
0.3 grams left
half lives are normally written in years
it goes likt this
A=final amount
P=initila amount
t=time elapsed
h=time half life is (same units as time)
let's use days as the units of time
we are given
initial amount=1gram
final amount=0.3gram
time=4 days
so
solve for h
take the ln of both sides
times both sides by h
divide both sides by ln(0.3)
use calculator
h=2.30287
3 sig figs
h=2.303 days
1 gram left
0.3 grams left
half lives are normally written in years
it goes likt this
A=final amount
P=initila amount
t=time elapsed
h=time half life is (same units as time)
let's use days as the units of time
we are given
initial amount=1gram
final amount=0.3gram
time=4 days
so
solve for h
take the ln of both sides
times both sides by h
divide both sides by ln(0.3)
use calculator
h=2.30287
3 sig figs
h=2.303 days