Find the rate at Simple interest, at which a sum becomes four times of itself in 15 years.

Answer: Option C

Explanation:

$$\begin{aligned} \text{ S.I. = } \frac{P \times R \times T}{100} \end{aligned}$$
So, by putting the values in the above formula, our result will be.
$$\begin{aligned} \text{ Required result = } \frac{7000 \times 50 \times 9}{3 \times 12 \times 100} = 875 \end{aligned}$$

[Please note that we have divided by 12 as we converted 9 months in a year format]

Answer: Option A

Explanation:

Let the sum is 100.

As financier includes interest every six months., then we will calculate SI for 6 months, then again for six months as below:

SI for first Six Months = (100*10*1)/(100*2) = Rs. 5

Important: now sum will become 100+5 = 105

SI for last Six Months = (105*10*1)/(100*2) = Rs. 5.25

So amount at the end of year will be (100+5+5.25)
= 110.25

Effective rate = 110.25 - 100 = 10.25

Answer: Option D

Explanation:

We need to calculate the total amount to be paid by him after 4 years, So it will be Principal + simple interest.

So,
$$\begin{aligned} => 500 + \frac{500*5*4}{100} => Rs. 600 \end{aligned}$$

Answer: Option B

Explanation:

Let the present worth be Rs.x
Then,S.I.= Rs.(132 - x)

=› (x*5*2/100) = 132 - x

=› 10x = 13200 - 100x

=› 110x = 13200

x= 120

Answer: Option B

Explanation:

Lets assume that three parts are x, y and z.
Simple Interest, R = 5%

From question we can conclude that, x + interest (on x) for 2 years = y + interest (on y) for 3 years = z + interest (on y) for 4 years

$$\begin{aligned} \left( x + \frac{x*5*2}{100} \right) = \left( y + \frac{y*5*3}{100} \right) = \left( z + \frac{z*5*4}{100} \right)\\ \left( x + \frac{x}{10} \right) = \left( y + \frac{3y}{20} \right) = \left( z + \frac{z}{5} \right) \\ => \frac{11x}{10} = \frac{23y}{20} = \frac{6z}{5} \\ \text{lets assume k = }\frac{11x}{10} = \frac{23y}{20} = \frac{6z}{5} \\ \text{then }x = \frac{10k}{11} \\ y = \frac{20k}{23}\\ z = \frac{5k}{6}\\ \text{we know x+y+z = 2379}\\ => \frac{10k}{11} + \frac{20k}{23} + \frac{5k}{6} = 2379\\ \text{10k*23*6+20k*11*6+5k*11*23=2379*11*23*6}\\ \text{1380k+1320k+1265k=2379*11*23*6}\\ \text{3965k=2379*11*23*6}\\ k = \frac{2379*11*23*6}{3965}\\ \text{by putting value of k we can get x} \\ x = \frac{10k}{11} \\ =>x = \frac{10}{11}*\frac{2379*11*23*6}{3965}\\ =>x = \frac{10*2379*23*6}{3965}\\ = \frac{2*2379*23*6}{793}\\ = 2 * 3 * 23 * 6 = 828 \end{aligned}$$