Answer:
m_r = 125 g
Step-by-step explanation:
Formula to calculate the remaining mass is;
m_i = m_r × 2^(t/λ)
Where;
m_i is initial mass of sample
m_r is remaining mass after time t.
t is time
λ is half life.
We are given;
m_i = 1000 g
t = 15.9 years
λ = 5.3 years
Thus;
1000 = m_r × 2^(15.9/5.3)
1000 = 8m_r
m_r = 1000/8
m_r = 125 g