Formula : 1 Mark
Application : 1 Mark
Calculation : 2 Marks
Here, Principal P = Rs. 64000, Amount A = Rs 68921, rate R=5% per annum.
Since the interest is compounded half - yearly.
∴A=P(1+R200)2n
⇒68921=64000(1+5200)2n
⇒6892164000=(4140)2n
⇒(4141)3=(4140)2n=3⇒n=32 years=112 years