Question

In class IX, the average of marks in science for six students was 48. After result declared, it was found in case of one student, the marks 45 were misread as 54. The correct average is :

• A. 46.40
• B. 46.50
• C. 76.50
• D. 64.39

Answer 1

Answer:

B. 46.50

olution: Given: Average marks of six students are 48. The mark 45 is misread as 54. Concept Used: Average = (Sum of all entry)/(Number of total entry) Calculation: Average marks of six students are 48 Total marks of six students = 48 × 6 ⇒ 288 The mark 45 is misread as 54 Sum of numbers of five students is (288 – 54) = 234 Actual sum of marks of six students = (234 + 45) ⇒ 279 The correct average = (279/6) ⇒ 46.5 ∴ The correct average is 46.5 Shortcut Trick Wrongly more number counted = (54 – 45) = 9 By mistake average increased by 9/6 = 1.5 The correct average = (48 – 1.5) ⇒ 46.5 ∴ The correct average is 46.5