Study Material — 13 PYQs (2020–2020) · Concept Notes · Shortcuts
IBPS RRB PO Simple Interest is a frequently tested subtopic — 13 previous year questions from 2020–2020 papers are included below with concept notes, key rules and shortcut tricks.
13 questions from actual IBPS RRB PO papers · all shown free · click option to reveal solution
Exam Q 12020Previous Year Pattern
Priya lent ₹12,000 to her friend at 6% simple interest per annum. After how many years will the interest amount to ₹2,160?
Exam Q 22020Previous Year Pattern
At what rate of simple interest per annum will ₹4,500 amount to ₹5,400 in 4 years?
Exam Q 32020Previous 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 42020Previous Year Pattern
Arun deposited ₹9,000 in a savings account at 7% simple interest per annum. How much total amount will he have after 2 years?
Exam Q 52020Previous Year Pattern
A loan of ₹15,000 is taken at 5% simple interest per annum. What is the simple interest for the first 6 months?
Exam Q 62020Previous Year Pattern
Two friends, Amit and Bhavna, each invested ₹8,000 in a bank. Amit's money earned ₹1,920 as simple interest in 4 years. At the same rate, how much interest will Bhavna earn in 5 years?
Exam Q 72020Previous Year Pattern
Rajesh invested ₹12,000 at 9% per annum simple interest. After how many years will the interest earned be ₹5,400?
Exam Q 82020Previous Year Pattern
A bank offers 7% simple interest per annum. If Priya deposits ₹15,000 and wants to earn ₹3,150 as interest, for how many months should she keep the money?
Exam Q 92020Previous Year Pattern
A sum of ₹9,000 is invested at 8% simple interest per annum. In how many years will the total amount (principal + interest) become ₹11,880?
Exam Q 102020Previous Year Pattern
Vikram borrowed ₹20,000 from a lender at 10% simple interest per annum. He repaid ₹4,000 after 2 years. How much more does he owe after 2 years (including the interest accrued)?
Exam Q 112020Previous Year Pattern
Meera lent ₹5,000 to Neha at 8% simple interest per annum. After 2 years, Neha returned the amount with interest. Meera then lent this entire amount to Priya at 10% per annum for 3 years. How much interest did Meera earn in total from both transactions?
Exam Q 122020Previous Year Pattern
A certain sum of money is lent at simple interest. If the rate of interest is increased by 2% per annum, the interest earned in 5 years increases by ₹500. What is the principal amount?
Exam Q 132020Previous Year Pattern
A sum of money becomes ₹18,000 in 4 years and ₹22,500 in 7 years at 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