Classs mean

The class size is 30 students. Math was not worse than mark 2. Find the number of pupils who were marked one if the class had a 1.4 average mark.

Correct answer:

a =  18

Step-by-step explanation:


a+b= 30
a+2b = 1.4 ·30

a+b= 30
a+2·b = 1.4 ·30

a+b = 30
a+2b = 42

Row 2 - Row 1 → Row 2
a+b = 30
b = 12


b = 12/1 = 12
a = 30-b = 30-12 = 18

a = 18
b = 12

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