The table shows the percentage of marks obtained by seven students in six different subjects in an examination. The numbers in the brackets are the maximum marks in each subject. Student Subject (Max. Marks in percentage) Maths (150) Chemistry (130) Physics (120) Geography (100) History (60) Computer Science (40) A 90 50 90 60 70 80 B 100 80 80 40 80 70 C 90 60 70 70 90 70 D 80 65 80 80 60 60 E 80 65 85 95 50 90 F 70 75 65 85 40 60 G 65 35 50 77 80 80 What are the average marks obtained by all the seven students in Mathematics? (Correct to two decimal places) Correct Answer 123.21 Short trick∶ Total sum of percentage = 90 + 100 + 90 + 80 + 80 + 70 + 65 = 575% ⇒ Average = 575/7 % ∴ Required percentage = 575/7 × 150/100 = 123.21 Detailed solution∶ Total sum of marks = (90% of 150) + (100% of 150) + (90% of 150) + (80% of 150) + (80% of 150) + (70% of 150) + (65% of 150) ⇒ 135 + 150 + 135 + 120 + 120 + 105 + 97.5 ⇒ 862.5 ∴ Required average marks = 862.5/7 = 123.21