Study Material — 14 PYQs (2019–2019) · Concept Notes · Shortcuts
SSC MTS Simple Interest is a frequently tested subtopic — 14 previous year questions from 2019–2019 papers are included below with concept notes, key rules and shortcut tricks.
14 questions from actual SSC MTS papers · all shown free · click option to reveal solution
Exam Q 12019Previous Year Pattern
Arun invested ₹20,000 at 6% simple interest per annum. What will be the total amount after 4 years?
Exam Q 22019Previous Year Pattern
If ₹15,000 amounts to ₹18,600 at simple interest in 2 years, what is the rate of interest per annum?
Exam Q 32019Previous 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 42019Previous Year Pattern
Priya lent ₹8,000 to her friend at 5% simple interest per annum. After how many years will the interest amount to ₹2,000?
Exam Q 52019Previous Year Pattern
A sum of ₹12,000 becomes ₹15,600 in 3 years at simple interest. What is the rate of interest per annum?
Exam Q 62019Previous Year Pattern
A sum of ₹8,000 is invested at a simple interest rate of 12% per annum. How much interest will be earned in 3 years and 6 months?
Exam Q 72019Previous Year Pattern
Two sums of money are in the ratio 3:4. If both are invested at 10% simple interest per annum, after 5 years the difference in their interests will be ₹500. What is the larger sum?
Exam Q 82019Previous Year Pattern
A person invests ₹12,000 at 7.5% simple interest per annum. In how many months will the interest earned be ₹1,800?
Exam Q 92019Previous Year Pattern
Ravi borrowed ₹15,000 at 8% simple interest per annum. After how many years will the total amount (principal + interest) become ₹19,800?
Exam Q 102019Previous Year Pattern
Priya lent ₹20,000 to Rahul at 9% simple interest per annum. Rahul repaid ₹2,700 as interest after some time. For how many months did Rahul borrow the money?
Exam Q 112019Previous Year Pattern
A sum of money becomes ₹6,600 in 4 years and ₹7,200 in 6 years under simple interest. What is the principal amount?
Exam Q 122019Previous Year Pattern
Priya lent ₹12,000 to Anita at 8% p.a. simple interest for 3 years. Anita then lent this entire amount (principal + interest) to Bhavna at 10% p.a. simple interest for 2 years. How much profit did Anita make in this transaction?
Exam Q 132019Previous Year Pattern
A certain sum of money is lent at simple interest. If the rate of interest is increased by 2% per annum, the simple interest for 5 years increases by ₹500. What is the principal?
Exam Q 142019Previous Year Pattern
Vikram invested ₹10,000 at 6% p.a. simple interest for 2 years. Deepak invested the same amount at 5% p.a. simple interest for 3 years. What is the difference in the simple interest earned by both?
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