# Shortcut Rules to Solve Problems on Simple Interest

## Effective for IBPS PO - SBI PO Exam

Here we have started a series of Quantitative Aptitude Shortcut Tricks for your upcoming SBI, IBPS, SSC and Other Government Competitive Exams. We will try to cover up all important topics of the quantitative Aptitude Sections from which question was generally asked.

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Trick - 1
• A certain sum is invested for certain time. It amounts to Rs.A1 at r1% per annum. But when invested at r2% per annum, it amounts to Rs.A2, then the sum is given by Rs.

$\left( \frac{{{A}_{2}}{{r}_{1}}-{{A}_{1}}{{r}_{2}}}{{{r}_{1}}-{{r}_{2}}} \right)$

Trick - 2
• If a certain sum of money amounts to Rs.A1 in t1, years and to Rs.A2 in t2 years, then the sum is given by
$\left( \frac{{{A}_{2}}{{t}_{1}}-{{A}_{1}}{{t}_{2}}}{{{t}_{1}}-{{t}_{2}}} \right)$
Trick -3
• A sum was put at SI at a certain rate for t years. Had it been put at x% lower rate, it would have fetched Rs. A less, then the sum is Rs.
$\left( \frac{A\times 100}{t\times x} \right)$
Trick - 4
• At a certain rate of simple interest Rs.X amounted to Rs.A in t1 years. If the rate of interest be decreased by r%, then after t2 years the new interest is given by Rs.
$\left[ \left( \frac{A-X}{{{t}_{1}}} \right)-\left( \frac{rX}{100} \right) \right]{{t}_{2}}$
Trick - 5
• The simple interest on a sum of money will be Rs.X after t1 years. If in the next t2 years principal becomes n times, then the total interest at the end of (t1+t2)th year is given by Rs.
$x\left[ 1+\left( \frac{{{t}_{2}}}{{{t}_{1}}} \right)n \right]$
Trick -6
• If a sum of money becomes 'n' times at the simple interest rate of r% per annum, then it will become 'm' times at the simple interest of
$\left[ \left( \frac{m-1}{n-1} \right)r \right]percent$

Questions for Practice

Q1. A certain sum is invested for certain time. It amounts to Rs.80 at 5% per annum. But when invested at 2% per annum, it amounts to 40. Find the sum.

Q2. A certain sum of money amounts to Rs. 756 in 2 years and to Rs.873 in 3.5 years. Find the sum and rate of interest.

Q3. A sum was put at SI at a certain rate for 2 years. Had it been put at 3% lower rate, it would have fetched Rs.300 less. Find the sum.

Q4. At a certain rate of simple interest Rs.800 amounted to Rs.920 in 3 years. If the rate of interest be decreased by 3% what will be amount after 3 years ?

Q5. The simple interest on a sum of money will be Rs 300 after 4 years. In the next  years principal becomes 4 time, what will be the total interest at the end the 10th years?

Q6. A sum of money becomes four times at the simple interest rate of 5% per annum. At what rate percent will it become savenfold?

Answer 1. $13\frac{1}{3}$ 