Directions: Each of the questions given below consists of a statement and/or a question and two statements numbered I and II given below it. You have to decide whether the data provided in the statement(s) is/are sufficient to answer the question. Read both the statements and Give answer (a) if the data in statement I alone are sufficient to answer the question while the data in statement II alone are not sufficient to answer the question; Give answer (b) if the data in statement II alone are sufficient to answer the question while the data in statement I alone are not sufficient to answer the question; Give answer (c) if the data either in statement I or in statement II alone are sufficient to answer the question; Give answer (d) if the data even in both statements I and II together are not sufficient to answer the question; Give answer (e) if the data in both statements I and II together are necessary to answer the question. By what percent is the salary of the elder son more than that of the younger son? I. The father's salary is less than that of the elder son by 37%. II. His salary is less than that of the younger son by 30%.

Concept & Logic To find a percentage difference or percentage increase between two unknown variables, we only need to establish their ratio, not their absolute monetary values. Percentage Increase = $\frac{\text{Elder} - \text{Younger}}{\text{Younger}} \times 100$ Step-by-Step Solution Calculation / Deduction: * Checking Statement I: Let Father's salary = $F$, Elder's = $E$, Younger's = $Y$. The father's salary is less than the elder son's by $37\%$. This gives the equation $F = E - 0.37E = 0.63E$. This relates $F$ and $E$, but tells us absolutely nothing about the younger son ($Y$). Insufficient alone. * Checking Statement II: "His salary" refers to the Father. The father's salary is less than the younger son's by $30\%$. This gives $F = Y - 0.30Y = 0.70Y$. This relates $F$ and $Y$, but tells us nothing about the elder son. Insufficient alone. * Combining both statements: We now have $F = 0.63E$ and $F = 0.70Y$. * Equating them gives $0.63E = 0.70Y$, which simplifies to establishing the ratio $\frac{E}{Y} = \frac{0.70}{0.63} = \frac{10}{9}$. * With the exact ratio known, the precise percentage difference can be calculated. Both statements are required to form this bridge. Exam Strategy & Shortcut Ratio Linking Method: Recognize that both sons' salaries are being directly compared to a common baseline (the Father's salary). When variable $A$ is related to $C$, and variable $B$ is related to $C$, you can mathematically always find the ratio between $A$ and $B$. Thus, recognize instantly that both statements combined will yield the answer. Common Pitfall Misinterpreting the phrasing "less than... by $37\%$". Some students incorrectly write $F = 0.37E$, rather than subtracting from $100\%$ to get $F = (1 - 0.37)E = 0.63E$. Always subtract from the base when a value is "less than" another. Final Answer **Therefore, the correct answer is If the data in both statements I and II together are necessary.**