Simple Interest Calculator - Problem

Calculate the simple interest and total amount given the principal amount, rate of interest per year, and time period in years.

Simple interest is calculated using the formula: SI = (Principal × Rate × Time) / 100

The total amount is: Total = Principal + Simple Interest

Return both the simple interest and total amount as floating point numbers with 2 decimal places precision.

Input & Output

Example 1 — Standard Loan

$ Input: principal = 5000, rate = 8, time = 3

› Output: [1200.0, 6200.0]

💡 Note: Simple Interest = (5000 × 8 × 3) / 100 = 1200. Total Amount = 5000 + 1200 = 6200

Example 2 — Short-term Investment

$ Input: principal = 1000, rate = 5, time = 2

› Output: [100.0, 1100.0]

💡 Note: Simple Interest = (1000 × 5 × 2) / 100 = 100. Total Amount = 1000 + 100 = 1100

Example 3 — High Interest Rate

$ Input: principal = 2500, rate = 12, time = 1

› Output: [300.0, 2800.0]

💡 Note: Simple Interest = (2500 × 12 × 1) / 100 = 300. Total Amount = 2500 + 300 = 2800

Constraints

1 ≤ principal ≤ 10⁶
0.1 ≤ rate ≤ 50
0.1 ≤ time ≤ 100

Visualization

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Asked in

T TCS 25 I Infosys 20 W Wipro 15 A Accenture 12

The key insight is to use the mathematical formula for simple interest: SI = (P × R × T) / 100. The optimal approach applies this formula directly instead of calculating year by year. Time: O(1), Space: O(1)

Common Approaches

✓ Direct Formula Application

⏱️ Time: O(1) Space: O(1)

Use the mathematical formula SI = (P × R × T) / 100 to calculate simple interest directly, then add to principal for total amount.

Step-by-Step Year Calculation

⏱️ Time: O(t) Space: O(1)

Calculate the interest earned each year by multiplying principal by rate, then sum all yearly interests. Finally add to principal for total amount.

Direct Formula Application — Algorithm Steps

Apply formula: SI = (principal × rate × time) / 100
Calculate total amount = principal + simple interest
Round both results to 2 decimal places

Visualization

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Step-by-Step Walkthrough

Apply Formula

SI = (5000 × 8 × 3) / 100 = 1200

Calculate Total

Total = Principal + SI = 5000 + 1200 = 6200

Result

Interest: $1200, Total Amount: $6200

Code -

solution.c — C

#include <stdio.h>
#include <math.h>

void solution(double principal, double rate, double time, double* interest, double* total) {
    double simpleInterest = (principal * rate * time) / 100;
    *interest = round(simpleInterest * 100) / 100;
    *total = round((principal + simpleInterest) * 100) / 100;
}

int main() {
    double principal, rate, time;
    scanf("%lf", &principal);
    scanf("%lf", &rate);
    scanf("%lf", &time);
    
    double interest, total;
    solution(principal, rate, time, &interest, &total);
    
    printf("[%.2f,%.2f]\n", interest, total);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

Constant time - only basic arithmetic operations

✓ Linear Growth

Space Complexity

O(1)

Only using a few variables to store results

✓ Linear Space

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Simple Interest Calculator - Problem

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Direct Formula Application — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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