Simple Interest, Compound Interest and Percentage questions form a major portion of the syllabus of various Government exams such as SSC CGL, SSC CHLS and many Railway Exams. Candidates must understand all the details about SI/CI & Percentage topic, the best way to tackle SI/CI & Percentage question, formulas, books needed and more.
Important SI/CI & Percentage Topics
Interest is the cost of taking up a loan or simply put; it is the cost of borrowing money. Interest is primarily of two types: Simple Interest and Compound Interest.
Simple Interest is calculated on the principal amount (original amount), borrowed by the borrower.
Compound Interest is calculated on the principal amount and the interest accumulated previously. Therefore, in simpler terms, it means that the compound interest is the interest on interest amount along with the principal amount.
The two concepts are essential for the preparation of competitive government examinations such as Staff Selection Commission (SSC) Exams, Railways Exams, etc., and even Bank examinations. The percentage is the rate or portion of something in comparison to the whole. Both Simple Interest and Compound Interest are concepts based on Percentage.
Simple Interest, Compound Interest and Percentage Formula
Simple Interest and Compound Interest Difference   Simple Interest is easier to calculate, and it remains constant through the life of the loan. Compound Interest has a more complex formula, and the amount of interest increases with each passing year.
 Simple Interest offers lower returns to the lender in comparison to Compound Interest.
 When anything has to be bought, Simple Interest is used as it is simpler to calculate. Compound Interest is useful, while one is investing.
 Principal Amount remains constant throughout the life of the loan if simple interest is levied. It varies throughout the life of the loan if Compound Interest is used.
 Growth is stagnant if Simple Interest is levied, and it is quite exponential and fast if Compound Interest is used.

Simple Interest Formula (Calculator)   Some key terms: A – Amount, P Principal Amount, R Rate of Interest, T Time for which the loan is taken.
 The formula for calculation of interest: P*R*T
 The formula for calculation of the amount to be returned along with interest: P + P*R*T.

Compound Interest Formula (Calculator)   Some key terms: A – Amount, P Principal Amount, R Rate of Interest, T Time for which the loan is taken.
 The formula for calculation of the amount to be returned along with interest: P(1+R)T
 The formula for calculation of interest: P(1+R)T  P

Percentage   If ‘x’ is a part of one whole thing ‘y’  then, the percentage of x in y is (x/y) 100

Tips to Solve/ Prepare for SI/CI & Percentage Questions
Some Important Simple Interest and Compound Interest Trips and Tricks SSC Exam. Check Simple Interest, Compound Interest and Percentage Shortcuts below.
 Suppose we have Compound Interest at the rate of a% for the 1st time interval and at the rate of b% for the second time interval. In that case, the net rate of interest after those two intervals will be calculated through = a + b + ab/100 (Assuming that the time intervals are equal).
 Difference between Simple Interest and Compound Interest for two years = PR2/ 1002
 Difference between Simple Interest and Compound Interest for three years = PR2(300+R)/ 1003
 If there is a sum of money that becomes Y times in n years at Compound Interest, it will become YP times in Pn years.
 Increase A by B % = A( 1+ B/100 )
 Decrease A by B % = A(1 – B/100)
 If there are successive percentage increases of a % and b%, the effective percentage increase is: {(a + b + (ab/100)}%
 If the price of an item goes up/down by y %, then the quantity consumed should be reduced by 100y/ (100 + y)% so that the total expenditure remains the same.
Simple Interest, Compound Interest and Percentage Problems and Solutions
Simple Interest and Compound Interest Quiz:
 If a loan of rupees 1000 was taken for two years on 10% interest, what will be the interest, and what will be the total amount which will have to be returned after two years?
A: 1000
B: 1100
C: 1200
D: 1300
Solution:
P = 1000
R = 10%
T = 2
Simple Interest = 1000 * 10/100 *2 = Rupees 200
Amount to be returned back after two years = 1000 + 200 = Rupees 1200
 A sum of rupees 1000 was borrowed for three years on a 10% Compound Interest Rate. What will be the interest, and what will be the total amount which will have to be returned after three years?
A: 329
B: 330
C: 331
D: 332
Solution:
P = 1000
T = 3
R = 10
Amount to be retuned = 1000 * (1+10/100)3 = Rupees 1331
Compound Interest = 1331 – 1000 = Rupees 331
 Mr Avinash spends 50% of his monthly income on grocery items and out of the remaining he spends 25% on travelling, 30% on entertainment, 15% on his pets and the remaining amount of Rs. 900 is saved. What is Mr Amar’s monthly income?
A: 6000
B: 9000
C: 8000
D: 7000
Grocery = 50%
Remaining = 50%
On Remaining amount he spends:
Travel = 25%
Entertainment = 30%
Pets = 15%
Total = 70% ⇒ Remaining = (100 – 70) % of 50%
Rest amount ⇒ 900 = 30% of 50%
⇒ 15% = 900
100% = 6,000.
Simple Interest and Compound Interest Questions for SSC CGL
Some of the most repeated Simple Interest and Compound Interest Questions are:
 The difference between CI and SI for three years is 992. If the rate of interest is 10%, what is the principal? – Answer = 32,000 Rupees.
 If the ratio of the difference between CI and SI for three years and two years is 31:10, then find the Rate of Interest? Answer = 10%
 In a camp of 60 cadets and five instructors, each cadet got kits that are 20% of the total number of cadets, and each instructor got kits that are 30% of the total number of cadets. How many kits were there? Answer = 810
Importance of Simple Interest, Compound Interest and Percentage in SSC exams
 These three topics of Simple Interest, Compound Interest and Percentage are very frequently asked in all the competitive government examinations.
 Candidates should practice such questions thoroughly as these are significantly less timeconsuming.
 These questions are very high scoring.
 These questions can be tricky to understand, but once, understood can give an edge over the competitors.
Recommended books for Simple Interest and Compound Interest and Percentage
Book  Importance of the book 
Rakesh Yadav Sir’s Advanced Math   This book has questions on the updated pattern of SSC.
 This book has the largest repository of practice questions for SSC.

Rajesh Verma, Arihant publication,  Fast Track Objective Arithmetic   This book has a very easy language to understand for students from a nonmathematical background.
 This book has a comprehensive series of practice questions.

RS Aggarwal, S Chand Publication  Quantitative Aptitude for Competitive Exams   This book has advanced level questions for students who are clear on the basics.
 This book has good explanations for the questions asked in SSC exams.

Why should you use BYJU'S Exam Prep for SI/ CI and Percentage?
BYJU'S Exam Prep is a full package for students who are keen on selfstudy. You don’t need to attend any coaching if you use the BYJU'S Exam Prep App. BYJU'S Exam Prep provides the highest number of practice questions for Simple Interest, Compound Interest and Percentage and also ensure that you are clear about the concept and required formulas.
They have an enormous SI/ CI and Percentage question bank. Along with practice questions, they also provide study material and also keep the user informed about the upcoming important dates. They also provide all of their students who have signed up on the app, with a series of previous years question papers. It is one full package that is offered at very studentfriendly prices.
Frequently Asked Questions from Simple Interest, Compound Interest and Percentage topics for SSC Exams.
Ques: Do past year question papers help in preparation for the exam and particularly Simple Interest and Compound Interest Questions?
Yes, past year papers are highly beneficial. They provide an idea of the type of questions that can be asked in the exam.
Ques: What should I do, if I find myself very weak in SI & CI Questions?
These are the core concepts; you cannot neglect them. You need to focus on the foundational concept of the percentage to understand these two concepts.
Ques: How to approach a question based on SI/ CI and Percentage?
Understanding the language of the questions is the most important part. Reading the question twice and understanding what the examiner wants should always be the first task.
Ques: How to prepare for these topics if only three months are left before the exams?
Solve all the questions from whichever book you are using and attempt mock tests for each individual topic.