Answer:
60.5 milligrams per square centimeter First, determine how many half lives have expired by dividing the time by the half-life. So: 55/20 = 2.75 That means that only 2^(-2.75) = 0.148650889 = 14.8650889% of the original substance remains. So just divide the amount remaining by 0.148650889 to get the original amount. 9 / 0.148650889 = 60.5445419 So originally, there was 60.5 milligrams per square centimeter 55 years ago.
Answer:
Just add the painted miles
2 1/6 + 1 2/3
=3 5/6
then we subtact the total miles that wanna be painted which is 6
6 - 3 5/6
=2 1/6
The answer B
Note:
sin(-θ) = -sinθ
sin(-15°) = -sin15° Use a calculator
sin(-15°) = -sin15° = -0.2588
sin(-15°) = -0.2588