# Simple Interest Questions

**FACTS AND FORMULAE FOR SIMPLE INTEREST QUESTIONS**

**1. Principal:** The money borrowed or lent out for a certain period is called the **principal **or the **sum**.

**2. Interest:** Extra money paid for using other's money is called **interest**

**3. Simple Interest (S.I.) : **If the interest on a sum borrowed for a certain period is reckoned uniformly, then it is called **simple interest.**

Let Principal = P, Rate = R% per annum (p.a.) and Time = T years. Then,

(i) $S.I=\left(\frac{P\times T\times R}{100}\right)$

(ii) $P=\left(\frac{100\times S.I}{R\times T}\right);R=\left(\frac{100\times S.I}{P\times T}\right)andT=\left(\frac{100\times S.I}{P\times R}\right)$

A) 0.1% | B) 0.2% |

C) 0.3% | D) 0.4% |

Explanation:

(1500 x R1 x 3)/100

=> 4500 (R1-R2) = 1350

=> (R1-R2)= 1350/4500 = 0.3 %

A) Rs.1200 | B) Rs.1300 |

C) Rs.1400 | D) Rs.1500 |

Explanation:

At 5% more rate, the increase in S.I for 10 years = Rs.600 (given)

So, at 5% more rate, the increase in SI for 1 year = 600/10 = Rs.60/-

i.e. Rs.60 is 5% of the invested sum

So, 1% of the invested sum = 60/5

Therefore, the invested sum = 60 × 100/5 = Rs.1200

A) 65years | B) 56years |

C) 45years | D) 57years |

Explanation:

Simple interest is given by the formula SI = (pnr/100), where p is the principal, n is the numberof years for which it is invested, r is the rate of interest per annum

In this case, Rs. 1250 has become Rs.10,000.

Therefore, the interest earned = 10,000 – 1250 = 8750.

8750 = [(1250 x n x 12.5)/100]

=> n = 700 / 12.5 = 56 years.

A) Rs.16000 | B) Rs.12000 |

C) Rs.15000 | D) Rs.13000 |

Explanation:

Let the sum at 15% be Rs x and that at 18% be Rs (24000 - x).

{(x * 15 * 1)/100 } + { [(24000 – x) * 18 * 1]/100 } = 4050

or 15 x + 432000 - 18x = 405000 or x = 9000.

Money borrowed at 15% = Rs 9000 .

Money borrowed at 18% = Rs 15000.

A) 5% | B) 8% |

C) 12% | D) 15% |

Explanation:

S.I. for 3 years = Rs. (12005 - 9800) = Rs. 2205.

S.I. for 5 years = Rs.$\frac{2205}{3}\times 5$= Rs.3675

Principle = Rs.(9800-3675) = Rs.6125

Hence, Rate = $\left[\frac{100\times 3675}{6125\times 5}\right]$ =12%

A) Rs. 100 | B) Rs. 105 |

C) Rs. 115 | D) Rs. 110 |

Explanation:

Amount to be paid = $Rs.\left[100+\frac{200\times 5\times 1}{100}+\frac{100\times 5\times 1}{100}\right]$= Rs. 115**.**

A) Rs. 1800 | B) Rs. 2000 |

C) Rs. 1400 | D) Rs. 1250 |

Explanation:

2500 in 5th year and 3000 in 7th year

So in between 2 years Rs. 500 is increased => for a year 500/2 = 250

So, per year it is increasing Rs.250 then in 5 years => 250 x 5 = 1250

Hence, the initial amount must be 2500 - 1250 = Rs. 1250

A) 25years | B) 15years |

C) 20years | D) 22years |

Explanation:

From the information provided we know that,

Principal + 8% p.a. interest on principal for n years = 180 …….. (1)

Principal + 4% p.a. interest on principal for n years = 120 ……… (2)

Subtracting equation (2) from equation (1), we get

4% p.a. interest on principal for n years = Rs.60.

Now, we can substitute this value in equation (2),

i.e Principal + 60 = 120

= Principal = Rs.60.

We know that SI = , where p is the principal, n the number of years and r the rate percent of interest.

In equation (2), p = Rs.60, r = 4% p.a. and the simple interest = Rs.60.

Therefore, 60 =(60*n*4)/100

=> n = 100/4 = 25 years.