# 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

**Explanation : **

Original Expression:

10 + 30 – 100 x 50 / 25

**Replacing each operator simultaneously:**

The plus sign (+) becomes minus (-)

The minus sign (-) becomes multiply (x)

The multiply sign (x) becomes divide (/)

The divide sign (/) becomes plus (+)

After replacing all operators at once, the expression becomes:

10 – 30 x 100 / 50 + 25

## Now let’s solve this expression following standard order of operations:

First step: Work out multiplication

30 x 100 equals 3000

Second step: Work out division

3000 / 50 equals 60

Third step: The expression is now

10 – 60 + 25

Fourth step: Work from left to right with subtraction and addition

10 minus 60 equals -50

-50 plus 25 equals -25

Therefore, the final answer is -25