Answer:
Original Mass before 5 days = 82.97 gm
Explanation:
The problem can be solved using simple formula:
How much mass remains = (1 / 2^n) x Original Mass ------ (1)
Since,
How much mass remains = 65.1 gm
n = Number of half-lives during the interval = 5 days / 14.3 days = 0.35
Original Mass = ?
Now, equation (1) implies:
⇒ 65.1 = ( 1 / 2^0.35 ) x Original Mass
⇒ 65.1 = (0.785) x Original Mass
⇒ Original Mass = 82. 97 gm
Alternatively, another formula is:
N(t) = No (1/2)^ (t / t1/2) ------- (2)
where,
Nt = Mass Remains
No = Initial Mass
t = Time
t1/2 = Half Life
Equation (2) implies:
⇒ 65.1 = No (1/2) ^ (5/14.3)
Solving above equation we get,
No = 82.97 gm
