Arithmetic aptitude :: Simple Interest :: General Questions

• Simple Interest - General Questions
• Simple Interest - Data Sufficiency 1
• Simple Interest - Data Sufficiency 2
• Simple Interest - Important Formulas and Facts

Principal :

The amount of money one borrows from a lender for a certain period of time is known as principal amount or the sum.

Interest :

Extra charge paid for the borrowed money is called Interest

Simple Interest (S.I.) :

Simple interest is a method to calculate the interest amount on a loan

Let Pricipal $=P$, Rate $=R\%$ per annum (p.a.) and Time $=N$ years. Then

(i) Simple interest (SI) $=\left(\frac{P\times N\times R}{100}\right)$

(ii) $P$ $=\left(\frac{100\times SI}{R\times N}\right)$ ; $R=\left(\frac{100\times SI}{P\times N}\right)$ and $N=\left(\frac{100\times SI}{P\times R}\right)$.

A sum of money becomes $\frac{41}{40}$ of itself in $\frac{1}{4}$ years at certain rate of simple interest. The rate of interest per annum is

Answer:

Explanation:

Let  $P=1$, $SI$ $=\frac{41}{40}-1$ $=\frac{1}{40}$

Rate % $=\frac{(100*SI)}{P\times N}$

$=\left(\frac{\frac{1}{40}\times 100}{1\times\frac{1}{4}}\right)$ = 10%

A certain amount earns SI of Rs. 1,750 after 7 years. Had the interest been 2% more, how much more interest would it have earned ?

Answer:

Explanation:

$SI$ $=\frac{(P\times R\times N)}{100}$ $\Rightarrow\frac{(P\times R\times 7)}{100}$  $=1750$

$\Rightarrow PR$ $= 25000$

$SI$ $=\frac{(P\times (R+2)\times 7)}{100}$         

Given  $\left\{\frac{(P\times (R+2)\times 7)}{100}\right\}$ $-\left\{\frac{(PR\times 7)}{100}\right\}$ $=SI-1750$

We have 1 equation in 2 variables. $\therefore$ R and P cannot determined.

Mr. Y gave some money at simple interest  and at the end of 10 years, got back twice the sum. The rate percent per annum is

Answer:

Explanation:

$P$ $=100$ becomes $200$ in $10$ years

$SI$ $=100$

$R$ $=\frac{(100\times SI)}{P\times N}$

$=\frac{(100\times 100)}{(100\times 10)}$ = 10%

What annual installment will discharge a debt of Rs. 1092 due in 3 years at 12% simple interest ?

Answer:

Explanation:

Let installment be $x$

Then $\left\{x+\frac{(x\times 12\times 1)}{100}\right\}$ $+\left\{x+\frac{(x\times 12\times 2)}{100}\right\}$ $+x$ $=1092$

$x$ = Rs.325

Two equal sums of money are lent at the same time at 9% per annum and 8% per annum simple interest respectively. The former is recovered 6 months earlier than the latter and the amount in each case is Rs. 17,680. Find the sum

Answer:

Explanation:

Let sum lent for interest in each case be Rs. $100$

Given $\frac{100\times\left(N-\frac{1}{2}\right)\times 9}{100}$ $=\frac{100\times N\times 8}{100}$

$\Rightarrow N$ $=\frac{9}{2}$ $=4\frac{1}{2}$ Yrs

If $P=100$ then Total Amount  $=100$ $+\left\{\frac{(100\times 8\times 9)}{(100\times 2)}\right\}$  $=136$

If $136$ is Total Amount then lent $=100$

If $17,680$ is Total Amount  then,

Lent $=\frac{(17680\times 100)}{136}$ = Rs.13,000

• Simple Interest - General Questions
• Simple Interest - Data Sufficiency 1
• Simple Interest - Data Sufficiency 2