Study Material — 17 PYQs (2019–2019) · Concept Notes · Shortcuts
SBI PO Simple Interest is a frequently tested subtopic — 17 previous year questions from 2019–2019 papers are included below with concept notes, key rules and shortcut tricks.
17 questions from actual SBI PO papers · all shown free · click option to reveal solution
Exam Q 12019Previous Year Pattern
A sum of ₹8,000 earns ₹1,600 as simple interest in 4 years. What is the rate of interest per annum?
Exam Q 22019Previous Year Pattern
At what rate per annum will ₹12,000 amount to ₹15,600 in 3 years under simple interest?
Exam Q 32019Previous Year Pattern
Priya invested ₹20,000 at 6% simple interest per annum. In how many years will the interest earned be ₹7,200?
Exam Q 42019Previous Year Pattern
A person borrowed ₹10,000 at 5% per annum simple interest. What will be the total amount to be repaid after 2.5 years?
Exam Q 52019Previous Year Pattern
Rajesh borrowed ₹5,000 at a simple interest rate of 8% per annum. How much interest will he pay after 3 years?
Exam Q 62019Previous Year Pattern
Arun lent ₹15,000 to his friend at 4% per annum simple interest. After how many months will the interest be ₹600?
Exam Q 72019Previous Year Pattern
A sum of money becomes ₹6,600 in 2 years and ₹7,200 in 3 years under simple interest. What is the principal amount?
Exam Q 82019Previous Year Pattern
Priya lent ₹15,000 to her friend at 8% per annum simple interest. After 2.5 years, how much total interest will she receive?
Exam Q 92019Previous Year Pattern
A certain sum of money is lent at 10% per annum simple interest. If the interest earned in 4 years is ₹2,400, what is the principal?
Exam Q 102019Previous Year Pattern
Amit invested ₹20,000 in a savings scheme at 9% per annum simple interest. Bhavna invested ₹25,000 at 7% per annum simple interest. After 3 years, what is the difference in the interest earned by both?
Exam Q 112019Previous Year Pattern
A bank offers 6% per annum simple interest. If a customer deposits ₹12,000 and wants to earn ₹1,440 as interest, for how many months should the money be deposited?
Exam Q 122019Previous Year Pattern
Ramesh lent ₹15,000 to Suresh at 8% p.a. simple interest. After some time, Suresh returned ₹18,600 to clear the debt. For how many months did Suresh borrow the money?
Exam Q 132019Previous Year Pattern
Two equal sums of money are lent at 6% and 5% simple interest respectively. The first sum is recovered after 5 years and the second after 4 years. If the difference in the amounts recovered is ₹400, what is each sum?
Exam Q 142019Previous Year Pattern
A person invests ₹12,000 at 7.5% p.a. simple interest for a certain period. If he had invested ₹8,000 more at the same rate for 2 years less, he would have earned ₹1,200 less in interest. For how many years was the original amount invested?
Exam Q 152019Previous Year Pattern
Arun borrowed ₹50,000 from a bank at 9% p.a. simple interest. He repaid ₹20,000 after 2 years. How much should he pay after another 3 years to clear the entire debt?
Exam Q 162019Previous Year Pattern
A sum of money lent at simple interest amounts to ₹5,720 in 2 years and ₹7,140 in 5 years. At what rate per annum is the money lent?
Exam Q 172019Previous Year Pattern
A sum of money becomes ₹8,400 after 4 years and ₹9,600 after 7 years under simple interest. What is the principal amount?
Concept Notes
Simple Interest— Rules & Concept
Core ConceptRead this first — the foundation of the topic
Simple Interest is the extra money paid on borrowed money or earned on invested money. It is calculated only on the original amount (called Principal) for a specific time period at a fixed rate. Core Concept: Simple Interest remains constant every year. If you borrow Rs. 1000 at 10% simple interest, you pay Rs. 100 every year as interest. The principal amount never changes in calculations.
Formula BlockMemorise — at least one formula appears in every paper
Block:
Simple Interest (SI) = (P × R × T) / 100
Amount = Principal + Simple Interest
Principal (P) = (SI × 100) / (R × T)
Rate (R) = (SI × 100) / (P × T)
Time (T) = (SI × 100) / (P × R)
Exam PatternsWhat examiners ask — read before attempting PYQs
SSC CGL consistently asks 2-3 questions on Simple Interest. Common question types include finding SI when P, R, T are given, calculating time or rate when other values are known, and comparing simple vs compound interest scenarios.
Master Shortcut #1 - Quick SI Calculation:
For easy percentages, use direct multiplication:
- 10% of any amount = Amount/10
- 5% of any amount = Amount/20
- 20% of any amount = Amount/5
Worked ExampleSolve this step-by-step before moving on
1
Step 1
Identify P = 8000, R = 12%, T = 3 years
2
Step 2
Apply formula SI = (P × R × T) / 100
3
Step 3
SI = (8000 × 12 × 3) / 100
4
Step 4
SI = 288000 / 100 = Rs. 2880
5
Step 5
Amount = 8000 + 2880 = Rs. 10,880
Shortcut #2 - Time-Rate Relationship:
If rate doubles, time becomes half for same SI.
If time doubles, rate becomes half for same SI.
This helps eliminate wrong options quickly.
Worked Example 2:
Question: At what rate will Rs. 5000 amount to Rs. 6500 in 4 years at simple interest?
1
Step 1
Amount = 6500, Principal = 5000
2
Step 2
SI = Amount - Principal = 6500 - 5000 = Rs. 1500
3
Step 3
Using R = (SI × 100) / (P × T)
4
Step 4
R = (1500 × 100) / (5000 × 4)
5
Step 5
R = 150000 / 20000 = 7.5%
Shortcut #3 - Percentage Method:
When principal becomes 'n' times in 't' years:
Rate = [(n-1) × 100] / t
Example: If money doubles (n=2) in 10 years, Rate = (2-1) × 100/10 = 10%
Most Common Trap: Students often confuse the time unit. If rate is per annum but time is given in months, convert months to years by dividing by 12. Always match the time unit with the rate unit. This single mistake costs many marks in SSC CGL.
Another frequent error is adding interest multiple times. Remember, in simple interest, you add interest only once to get the final amount, unlike compound interest where interest compounds.
Key Points to Remember
Simple Interest formula: SI = (P × R × T) / 100 where P=Principal, R=Rate, T=Time
Amount = Principal + Simple Interest (add only once, not yearly)
SI remains constant every year unlike compound interest which grows
Quick calculation: 10% SI = Principal/10, 20% SI = Principal/5
If money becomes n times in t years, Rate = [(n-1) × 100] / t
Time and rate are inversely proportional for same SI amount
Always convert time units to match rate units (months to years or vice versa)
Principal can be found using: P = (SI × 100) / (R × T)
Rate doubles means time halves for same SI amount earned
Common trap: Never compound the interest in simple interest problems
Exam-Specific Tips
Standard SI formula uses division by 100, never by 1000 or other numbers
When rate is given per annum, time must be in years for direct calculation
If principal doubles, the rate-time product always equals 100
SI for 2 years at 10% rate equals 20% of principal amount
Principal formula derivation: P = (SI × 100) / (R × T)
Rate formula: R = (SI × 100) / (P × T) gives percentage value
Time formula: T = (SI × 100) / (P × R) gives time in rate's unit
Amount formula: A = P + SI = P[1 + (R × T)/100]
60-Second Revision — Simple Interest
Formula: SI = (P × R × T) / 100, Amount = P + SI
Remember: Always match time units with rate units before calculation
Shortcut: 10% rate means SI = Principal × Time ÷ 10
Trap: Never add interest multiple times in simple interest
Quick check: If money doubles in t years, rate = 100/t percent
Inverse relation: Rate doubles, time halves for same SI
Convert months to years by dividing by 12 when rate is per annum