Question

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A class average mark in an exam is 70. The average of students who scored below 60 is 50. The average of students who scored 60 or more is 75. If the total number of students in this class is 20, how many students scored below 60?

Answer 1

Answer:

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Answer 2

Step-by-step explanation:

Let n the number of students who scored below 60 and N the number of students who scored 60 or more.

Xi the grades below 60 and

Yi the grades 60 or more.

Average class → $\frac{Sum(Xi) \: + \: Sum(Yi)}{ 20 }$ = 70

Average for less than 60 → $\frac{ Sum(Xi) }{n}$ = 50

Average for 60 or more → $\frac{ Sum(Yi) }{N}$ = 75

→ 50n + 75N = 1400

Total number of students → n + N = 20

• n = 4 and N = 16