Practice Test Discussion

Q)

The mean weight of 34 students of a school is 42 kg. If the weight of the teacher is included, then the mean rises by 400 g. Find the weight (in kg) of the teacher?

[RRB, 2015]


  • Explanation

    Here we can use the formula

    Average (A)=Sum of observations (S)No. of observations (N) ⇒ S=A×N

    According to the question,

    Sum of weight of 34 students (A=42, N=34)

    ⇒S=42 X 34 =1428

    Later, Wieght of the teacher included, The mean rises by 400 g. (so A=42.4, N=35)

    So, sum of weight of 35 students

    ⇒S=42.4 X 35 =1484

    Now,

    The teacher's age =(sum of weight of 34 students)-(Sum of weight of 35 students)

       =1484-1428

       = 56

    Hence, Option B is correct.

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    Average

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