Question

In a History examination, the average for the entire class was 80 marks. If 10% of the students scored 95 marks and 20% scored 90 marks. What was the average marks of the remaining students of the class

Answer 1

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Let n be the total number of students

Average marks = 80 = Total marks /n

10% has scored 95

M1 =(10/100×n)×95=95n/10 (total marks of 10% of students)

20% has scored 90

M2 =(20/100×n) × 90 = 180n/10

rest 70% 100 − 10 − 20 scores x

M3 = (70/100×n)x=7nx/10  

total marks = M1 + M2 + M3 = (275+7x/10)n 

⟹ 80 = Total / n = 275 + 7x / 10

⟹ 800 = 275 + 7x

⟹ x = 75

∴ rest of the class has scored 75