Mathematical Operations

1. A. SPRQ
2. B. QRPS
3. C. QRSP
4. D. SPQR

Answer: B

Explanation

This question requires substituting the given symbols for mathematical operations and then evaluating the expression using the order of operations (BODMAS/PEMDAS).
Given: P = +, Q = –, R = ×, S = ÷. Equation: 60_15_3_20_4 = 20.

Let’s test each option:
(a) SPRQ: 60 ÷ 15 + 3 × 20 – 4 = 4 + 60 – 4 = 60. (Incorrect)
(b) QRPS: 60 – 15 × 3 + 20 ÷ 4 = 60 – 45 + 5 = 15 + 5 = 20. (Correct)
(c) QRSP: 60 – 15 × 3 ÷ 20 + 4 = 60 – (45/20) + 4 = 60 – 2.25 + 4 = 61.75. (Incorrect)
(d) SPQR: 60 ÷ 15 + 3 – 20 × 4 = 4 + 3 – 80 = 7 – 80 = -73. (Incorrect)

Only option (b) results in 20, making it the correct answer. This question assesses basic arithmetic operations and the ability to follow a given set of rules, a common type in UPSC CSAT’s logical reasoning section.

1. A. 15
2. C. –15
3. D. –25

Answer: D

Explanation

First, replace the mathematical operations in the given expression according to the provided rules:
Original expression: 10 + 30 – 100 x 50 ÷ 25

Applying the rules:
– ‘+’ becomes ‘–’
– ‘–’ becomes ‘x’
– ‘x’ becomes ‘÷’
– ‘÷’ becomes ‘+’

The transformed expression is: 10 – 30 x 100 ÷ 50 + 25

Now, follow the standard order of operations (BODMAS/PEMDAS):
1. **Division**: 100 ÷ 50 = 2
The expression becomes: 10 – 30 x 2 + 25
2. **Multiplication**: 30 x 2 = 60
The expression becomes: 10 – 60 + 25
3. **Addition and Subtraction** (from left to right):
10 – 60 = -50
-50 + 25 = -25

The value of the expression is -25. This question tests logical reasoning by reinterpreting mathematical operations.