The monthly average salary for 8 employees plus one supervisor is ₹15,000. If the supervisor earns ₹25,000, what is the average salary of the 8 employees?

Correct — C. Rebuild the total, then take the supervisor out.

Total for 9 people: 9 × 15,000 = 1,35,000
Remove the supervisor: 1,35,000 − 25,000 = 1,10,000
Average of the 8: 1,10,000 ÷ 8 = ₹13,750 → option (c)

Check: the supervisor is 10,000 above 15,000, so the 8 average 10,000 ÷ 8 = 1,250 below it: 15,000 − 1,250 = 13,750

Why the others are wrong

• (a)
  ₹14,750 — ₹14,750 × 8 = ₹1,18,000, and adding the supervisor's ₹25,000 gives ₹1,43,000, more than the ₹1,35,000 that 9 × 15,000 allows.
• (b)
  ₹13,000 — ₹13,000 × 8 = ₹1,04,000, and with the supervisor's ₹25,000 that is ₹1,29,000, ₹6,000 short of 9 × 15,000.
• (d)
  ₹13,500 — ₹13,500 × 8 = ₹1,08,000, and with the supervisor's ₹25,000 that is ₹1,33,000, ₹2,000 short of 9 × 15,000.

Total = average × count. The ₹15,000 average covers all nine people, the 8 employees plus the supervisor, so their salaries add to 9 × 15,000.

Taking a known member out means subtracting that value from the total and dividing by the new count. The deviation method agrees: the supervisor's ₹10,000 above the average is balanced by the 8 employees sitting ₹1,250 each below it.

Key facts

• Total = average × number: 9 × 15,000 = ₹1,35,000.
• Deviations from an average add up to zero.
• 1,10,000 ÷ 8 = 13,750.

Common traps

• Multiplying 15,000 by 8 instead of 9: the average includes the supervisor.
• Dividing the remaining ₹1,10,000 by 9 instead of 8.

No directly related past PYQ was found.