The rate of simple interest of a bank increased from 10.5% to 18% and time duration is also increased from 4.5 years to 7 years. The total simple interest was increased by Rs. 1890. Find the increased simple interest.

3024

Let principal be P;

S.I. @ 10.5% in 4.5 years = \(\frac{P\;×\;10.5\;×\;4.5}{100}\) ---(i)

S.I. @ 18% in 7 years = \(\frac{P\;×\;18\;×\;7}{100}\) ---(ii)

Given, that increase in S.I. is ₨.1250,

(Subtracting eq. (i) from (ii))

⇒ 1890 = \(\frac{P\;×\;18\;×\;7}{100}\) - \(\frac{P\;×\;10.5\;×\;4.5}{100}\)

⇒ 1890 = \(\frac{9P}{100}\) [14 - \(\frac{21}{4}\)]

⇒ 1890 = \(\frac{9P}{100}\) [\(\frac{35}{4}\)]

⇒ P = \(\frac{1890\;×\;100\;×\;4}{9\;×\;35}\)  

⇒ P = ₨.2400

So, Increased Simple Interest = \(\frac{2400\;×\;18\;×\;7}{100}\) = ₨.3024