₹ 4000 amount to ₹ 5000 in 8 years. In what time will ₹ 1600 amount to ₹ 2400 at the same rate?
16 years
Principal (P) = ₹ 4000 ; Amount = ₹ 5000
Hence Interest (I) = ₹ 5000 - ₹ 4000 = ₹ 1000
Let the rate per annum be 'R'
Time (n)= 8 years
Now, I=PTR100
⟹1000 = 4000×8×R100
R=258 %
In the second case P = 1600 and Amount = ₹ 2400
Hence I = ₹ 2400 - ₹ 1600 = ₹ 800
Let the time be n and rate of interest = 258 %
Then, 800 = 1600×25×n100×8
⟹ n = 800×8×1001600×25
Therefore n = 16 years