Prelims 2024

Q. If a+b means a-b; a-b means axb; axb means a÷b; a÷b means a+b, then what is the value of 10+30-100 x 50÷25? (Operations are to be replaced simultaneously)

a) 15
b) 0
c) -15
d) -25
Correct answer: d) -25

Question from UPSC Prelims 2024 CSAT Paper

Explanation:

Let’s approach this step-by-step, replacing the operations as given in the question:

1) First, let’s replace the operations simultaneously:
10+30-100×50÷25 becomes 10-30×100÷50+25

2) Now, let’s solve this using the standard order of operations (PEMDAS):

a) First, division: 100÷50 = 2
10-30×2+25

b) Next, multiplication: 30×2 = 60
10-60+25

c) Now we can perform the operations from left to right:
10-60 = -50
-50+25 = -25

3) Therefore, the final answer is -25.

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