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In a primary school the average weight of male students is 65.9 kg and 27 Jan 2021, 04:00
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45% (medium)

Question Stats:

72% (02:29) correct 28% (03:08) wrong based on 186 sessions

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In a primary school the average weight of male students is 65.9 kg and the average weight of female students is 57 kg. If the average weight of all the students (both male and female) is 60.3 kg and the number of male students in the school is 66, what is the number of female students in the school?

(A) 112
(B) 116
(C) 118
(D) 160
(E) 180
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In a primary school the average weight of male students is 65.9 kg and 29 Jan 2021, 22:49
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Using mixture and allegation method

Ans A
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In a primary school the average weight of male students is 65.9 kg and 30 Jan 2021, 09:28
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Let the number of female students = x

Sum of ages of the male students = 65.9 * 66

Sum of ages of the female students = 57x

Therefore Average = 60.3 = Sum of observations / total observations = \(\frac{65.9 * 66 + 57x}{66 + x}\)

66 * 60.3 + 60.3x = 65.9 * 66 + 57x

3.3x = 66 * (65.9 - 60.3)

x = (660 / 33) * (5.6) = 20 * 5.6 = 112


Option A

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In a primary school the average weight of male students is 65.9 kg and 31 Jan 2021, 05:51
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Solution



Given
In this question, we are given that
    • In a primary school, the average weight of male students is 65.9 kg
    • The average weight of female students is 57 kg
    • The average weight of all the students (both male and female) is 60.3 kg
    • The number of male students is 66

To find
We need to determine
    • The number of female students

Approach and Working out
    • Male Students:
      o Number of male students = 66
      o Average weight of male students = 65.9 kg
         So, sum of the weights of the male students = 66 × 65.9 ----(1)

    • Female Students:
      o Number of male students = x
      o Average weight of female students = 57 kg
         So, sum of the weights of the female students = 57x -----(2)

    • Total Students:
      o Number of total students = 66 + x
      o Average weight of total students = 60.3 kg
         So, sum of the weights of all the students = (66 + x) × 60.3 -----(3)

Now, sum of the weights of all the students = sum of the weights of the male students + sum of the weights of the female students.

Combining (1), (2), and (3), we get:
    • (66 + x) × 60.3 = (66 × 65.9) + 57x
    • (66 × 60.3) + 60.3x = (66 × 65.9) + 57x
    • 60.3x – 57x = (66 × 65.9) - (66 × 60.3)
    • 3.3x = 66 × (65.9 – 60.3)
    • 3.3x = 66 × 5.6
    • x = (66 × 5.6)/3.3 = 112


Thus, option A is the correct answer.

Correct Answer: Option A
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In a primary school the average weight of male students is 65.9 kg and 24 Mar 2026, 02:24
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