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Question
A class consists of 50 students out of which 30 are girls. The mean of marks scored by girls in a test is 73 (out of 100) and that of boys is 71. Determine the mean score of the whole class.
Solution
Given, the number of girls out of 50 students = 30
∴ The number of boys out of 50 students = 50 – 30 = 20
Now, the marks obtained by 30 girls = 30 × 73 = 2190 and the marks obtained by 20 boys = 20 × 71 = 1420 ...[Mean of marks scored by girls in a test is 73 and that of boys is 71]
∴ Mean score of the whole class
= `("Marks obtained by 30 girls" + "Marks obtained by 20 girls")/("Number of girls" + "Number of boys")`
= `(2190 + 1420)/(20 + 30)`
= `3610/50`
= 72.2
Hence, the mean score of whole class is 72.2.
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