24
Q:

# A sum is being lent at 20 % per annum compound interest.what is the ratio of increase in amount of 4th year to 5th year?

 A) 4:5 B) 5:4 C) 5:6 D) can't be determined

Explanation:

$\inline&space;\frac{p\left&space;(&space;1+\frac{r}{100}&space;\right&space;)^4}{p\left&space;(&space;1+\frac{r}{100}&space;\right&space;)^5}=\frac{1}{\left&space;(&space;1+\frac{r}{100}&space;\right&space;)}$

= $\inline&space;\frac{100}{100+r}=\frac{100}{120}$  = $\inline&space;\frac{5}{6}$

Q:

Compound interest on a certain sum of money at 20% per annum for 2 years is Rs.5995. What is the SI on the same money at 8% per annum for 6 years ?

 A) Rs. 5989 B) Rs. 6540 C) Rs. 7844 D) Rs. 6789

Explanation:

Given C.I = 5984, R = 20% , T = 2yrs

$\inline \fn_jvn \small C.I=P\left [ \left ( 1+\left ( \frac{20}{100}\right )^{2} \right )-1 \right ]$

5984 = $\inline \fn_jvn \small C.I=P\left [ \left ( 1+\left ( \frac{20}{100}\right )^{2} \right )-1 \right ]$

=> P = (5995x25)/11

P = Rs. 13625

Now S.I = PTR/100

SI = (13625 x 8 x 6)/100 = Rs. 6540

1 38
Q:

At a certain rate of interest the compound interest of 3 years and simple interest of 5 years for certain sum of money is respectively Rs. 1513.2 and Rs. 2400. Find the common rate of interest per annum ?

 A) 5% B) 6% C) 4% D) 3%

Explanation:

Given compound interest for 3 years = Rs. 1513.2

and simple interest for 5 years = Rs. 2400

Now, we know that  C.I = $\inline \fn_jvn P\left [ \left ( 1+\frac{R}{100} \right )^{n}-1 \right ]$

=> 1513.2 = $\inline \fn_jvn P\left [ \left ( 1+\frac{R}{100} \right )^{3}-1 \right ]$ ...........(A)

And S.I = PTR/100

=> 2400 = P5R/100 ..................(B)

By solving (A) & (B), we get

R = 5%.

5 119
Q:

The compound interest earned by Sunil on a certain amount at the end of two years at the rate of 8% p.a. was Rs.2828.80. Find the total amount that Sunil got back at the end of two years in the form of principal plus interest earned  ?

 A) Rs. 11828.80 B) Rs. 19828.80 C) Rs. 9828.80 D) Rs. 19328.80

Explanation:

Let the sum be Rs. P
P{ $\inline \fn_jvn \small \left [ 1+\frac{8}{100} \right ]^{2}$ - 1 } = 2828.80

It is in the form of  $\inline \fn_jvn \small a^{2}-b^{2}=(a+b)(a-b)$

P(8/100)(2 + 8/100) = 2828.80

P = 2828.80 / (0.08)(2.08)

= 1360/0.08 = 17000

Principal + Interest = Rs. 19828.80

6 387
Q:

Find the C.I. on Rs. 15,225 for 9 months at 16% per annum compounded quarterly ?

 A) Rs. 1911 B) Rs. 1909 C) Rs. 1901 D) Rs. 1907

Explanation:

P = Rs. 15225, n = 9 months = 3 quarters, R = 16% p.a. per quarter.

Amount = $\inline \fn_jvn \small \left [ 15225x\left ( 1+\frac{4}{100} \right )^{3} \right ]$

= (15225 x 26/25 x 26/25 x 26/25) = Rs. 17126.05

=> C.I. = 17126 - 15625 = Rs. 1901.05.

3 338
Q:

The least number of complete years in which a sum of money put out at 20% C.I. will be more than doubled is  ?

 A) 3 years B) 4 years C) 2.5 years D) 2 years

$\inline \fn_jvn \small P(1 + 20/100)^{n}$ > 2P or $\inline \fn_jvn \small \left ( \frac{6}{5}\right )^{n}$ > 2