Correct Answer - Option 3 : 100 square meters
Given:
The average area of I and II room = 400 square meters
The average area of I, II, III room = 500 square meters
Area of IV room = Area of III room + 600 square meters
The average area of II, III and IV room = 900 square meters
Formula used:
Average = Sum of all the observation/Total number of observation
Calculation:
Area of (I + II) room = 800 ….. (1)
Area of (I + II + III ) = 1500 …..(2)
Area of (II + III + IV) = 2700 ….(3)
From (1) and (2)
⇒ 800 + III = 1500
⇒ III = 1500 – 800
⇒ III = 700
Area of IV room = 700 + 600
= 1300 square metres
From (3)
⇒ II +700 + 1300 = 2700
⇒ II = 2700 – 2000
⇒ II = 700 ….. (4)
From (1) and (4)
⇒ I + 700 = 800
⇒ I = 800 – 700
⇒ I = 100
∴ The area of I room is 100 square meters.