<span>As the age of the U-235 sample is 2.631 billion years, and the half-life of U-235 is 713 million years, the sample has undergone 2.361 X 1,000,000,000 / 713 X 1,000,000 = 3.69 half lives. In each half-life the sample reduces to half its original weight according to the radioactive Half-Life Formula:
ln (Nt /N0) = -kt, where N0 = mass of the original weight of radioactive material, Nt = mass of radioactive material at time t, k = decay constant and t = time interval . We have to put Nt/N0 = 1/2 for time interval = half-life.</span>
Answer:
a)15:6 b)2:3
Step-by-step explanation:
No. of used books=15-9=6
a) 15:6
b)
6:9
2:3
Rewrite the decimal number as a fraction with 1 in the denominator
0.225=0.22510.225=0.2251
Multiplying by 1 to eliminate 3 decimal places, we multiply top and bottom by 103 = 1000
0.2251×10001000=2251000
