Answer: 
Step-by-step explanation:
Given
Initial mass of radium is 
It decays by half every 6 years i.e. 
For radioactive decay, sample at any time is given by

Insert the values

Thus, option (b) is correct.
I believe that the answer is n+100- second choice
Answer:
B
Step-by-step explanation:
15% of 400 = x
.15 x 400 = x
X = 60 (tip)
400 + 60 = 460
Answer:

Explanation:
(3 × 10⁸) × 2 × 10³
3 × 10⁸ × 2 × 10³
3 × 2 × 10⁸ × 10³
6 × 10¹¹
In decimal: 600,000,000,000