Correct Answer: 4 yrs
Explanation:
Here , P= Rs 1000 T= 4 yrs R= 4 % where, P= Principal T= Time R= Rate Since , Simple Interest on Rs 1000=(1000 × 4 × 4)/100 = Rs 160now, simple interest=Rs 160 P = Rs 400 R = 10 % then, T=(100 × SI)/P × R = (100 × 160)/(400 × 10) = 4 yr