RRB Group-D Model Paper 14 with answers for online practice

Given:
A sum becomes 2 times in 4 years
Concept used:
Simple interest, SI = P × R × T/100
Calculation:
Amount = P + SI = 2P
SI = P
⇒ P = P × R × 4/100
⇒ R = 25%
Let in 't' years, the sum will become 16 times,
Amount = P + SI = 16P
SI = 15P
⇒ 15P = P × 25 × t/100
∴ t = 60 years
∴ The time taken is 60 years.