Answer:
About anything that adds up to 90...
Step-by-step explanation:
Answer:
47
Step-by-step explanation:
^
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:
Step-by-step explanation:
15 x 7 = 105
The gap is either 9 x 7 =63 or 12 x 7 = 84
105 - 84 = 21
105 - 63 = 42
So the shaded area is either is 21 or 42
