Single correct option
The monthly salaries of A and B are in the ratio 3 : 5. If each receives an increment of Rs 4,000, the ratio becomes 5 : 7. What is B's original monthly salary?
- A. Rs 8,000
- B. Rs 10,000
- C. Rs 12,000
- D. Rs 15,000
Show answer and solution
Answer: (B) Rs 10,000
Let the salaries be 3x and 5x.
(3x + 4000)/(5x + 4000) = 5/7 → 21x + 28000 = 25x + 20000 → 4x = 8000 → x = 2000.
B's salary = 5x = Rs 10,000.
Check: A = 6000, B = 10000; after the increment 10000 : 14000 = 5 : 7. ✓
Tip: When the same amount is added to both terms, the difference stays the same. Here the difference 2x becomes 2 parts of the new ratio. So 2x = 2k and 3x + 4000 = 5k gives x = k = 2000.
(3x + 4000)/(5x + 4000) = 5/7 → 21x + 28000 = 25x + 20000 → 4x = 8000 → x = 2000.
B's salary = 5x = Rs 10,000.
Check: A = 6000, B = 10000; after the increment 10000 : 14000 = 5 : 7. ✓
Tip: When the same amount is added to both terms, the difference stays the same. Here the difference 2x becomes 2 parts of the new ratio. So 2x = 2k and 3x + 4000 = 5k gives x = k = 2000.
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