Solution

Let the number of people who read ‘The Hindu and TOI (Only)’ be x Let the number of people who read ‘The Hindu and Economic Times (Only)’ be y. Let the number of people who read ‘TOI and Economics Times (Only)’ be z. Given that: 40 + 20 +x +y = 100 =>x+y = 40 ---- (i) 70 + 20 +x+z = 150 =>x+z = 60 ----(ii) 100 + 20 +y+z = 200 =>y+z = 80 -----(iii) Adding eq. (i), (ii) and (iii), we get 2 (x+y+z) = 180 x+y+x = 90 ----(iv) Now, subtracting (iv) by (i), we get z= 50 Now, subtracting (iv) by (ii), we get y= 30 Now, by subtracting (iv) by (iii), we get X=10 Required Average = (70+30+20)/3 = 120/3 = 40