Suresh starts working as an analyst with an annual salary of Rs. 1,60,000. He receives a 15% pay rise every year. After how many complete years will his annual salary become Rs. 2,79,841?

Introduction / Context:
This is a compound percentage growth problem involving annual salary increments. Suresh receives a fixed percentage raise each year, and we are asked to determine how many years it takes for his salary to reach a specified amount. This type of question mirrors real life salary growth scenarios and tests understanding of repeated percentage increases compounded over time.

Given Data / Assumptions:

• Initial annual salary = Rs. 1,60,000.
• Annual pay rise = 15% of the current salary.
• Final salary after some years = Rs. 2,79,841.
• We must find the number of complete years required.

Concept / Approach:
A salary that increases by a fixed percentage each year follows a compound growth pattern. If the initial salary is S and the growth rate per year is r, then after n years the salary is S * (1 + r)^n. Here, S = 160000 and r = 0.15. We need to find n such that 160000 * (1.15)^n = 279841. Since the options are discrete small numbers of years, it is efficient to compute the salary year by year and compare it with the target value.

Step-by-Step Solution:
Step 1: Initial salary in year 0 is 160000. Step 2: After 1 year: Salary = 160000 * 1.15 = 184000. Step 3: After 2 years: Salary = 184000 * 1.15 = 211600 (approximately). Step 4: After 3 years: Salary = 211600 * 1.15 ≈ 243340. Step 5: After 4 years: Salary = 243340 * 1.15. Step 6: Compute year 4 salary exactly: 160000 * (1.15)^4. Step 7: 1.15^2 = 1.3225, and 1.15^4 = 1.3225^2 ≈ 1.748. Step 8: 160000 * 1.748 ≈ 279680, and more accurate computation gives 279841. Step 9: Thus after 4 years, salary is Rs. 2,79,841, matching the given final salary.

Verification / Alternative check:
We can compute step by step more precisely. Year 1: 160000 * 1.15 = 184000. Year 2: 184000 * 1.15 = 211600. Year 3: 211600 * 1.15 = 243340. Year 4: 243340 * 1.15 = 279841 exactly. Since the fourth year value matches the target salary and earlier years are below it, we confirm that 4 years is the required duration.

Why Other Options Are Wrong:
3.5 years and 4.5 years are not meaningful in this context because increments are applied yearly and the question asks for complete years. After 3 years, the salary is 243340, which is still below 279841. After 5 years, the salary would exceed 279841, so 5 years is too long. The option "Cannot be determined" is incorrect because the information provided is sufficient to find the exact year count. Only 4 years fits the data.

Common Pitfalls:
Some learners may mistakenly apply simple interest style calculations, adding 15% of the original salary each year instead of compounding on the updated salary. Others might round too aggressively at intermediate steps, leading to a slightly different final salary and confusion. Using a structured compound interest formula or careful year by year multiplication avoids these errors.

Final Answer:
Suresh's annual salary becomes Rs. 2,79,841 after 4 yrs of working with 15% yearly increments.