In a team of 75 employees, the average monthly sales per employee is ₹ 1.8 lakh. If 30 junior employees average ₹ 1.2 lakh each, what is the average monthly sales figure (in ₹ lakh) for the senior employees?

Correct — B. Work with totals, not averages.

Team total = 75 × 1.8 = 135 lakh
Juniors' total = 30 × 1.2 = 36 lakh
Seniors' total = 135 − 36 = 99 lakh
Seniors = 75 − 30 = 45

Seniors' average = 99 ÷ 45 = 2.2 lakh → option (b)

Why the others are wrong

• (a)
  ₹4.2 lakh — At 4.2 lakh, the 45 seniors would total 189 lakh. Add the juniors' 36 and the team makes 225 lakh, an average of 3.0, not 1.8.
• (c)
  ₹2.8 lakh — At 2.8 lakh, seniors total 45 × 2.8 = 126 lakh. With the juniors' 36 the team makes 162 lakh, an average of 2.16, above the stated 1.8.
• (d)
  ₹2.7 lakh — At 2.7 lakh, seniors total 45 × 2.7 = 121.5 lakh. With the juniors' 36 the team makes 157.5 lakh, an average of 2.1, not 1.8.

An average is a total divided by a count, so group averages combine through their totals. Turn each average into a total, subtract the known group from the whole, and divide by the remaining head-count.

A deviation check gives the same answer. Each junior is 0.6 lakh below 1.8, a shortfall of 30 × 0.6 = 18 lakh. The 45 seniors must make it up: 18 ÷ 45 = 0.4 above 1.8, which is 2.2.

Key facts

• Total = average × number of members.
• Seniors' total here: 135 − 36 = 99 lakh, shared by 45 people.
• The shortfall below the overall average in one group equals the excess above it in the other.

Common traps

• Dividing the seniors' 99 lakh by 75, the whole team, instead of by the 45 seniors.
• Adding the juniors' 0.6 gap straight onto 1.8 (giving 2.4), which ignores that the groups are of different sizes.

No directly related past PYQ was found.