A school has four sections of chemistry in class XII having 40, 35, 45 and 42 students. The mean marks obtained in chemistry test are 50, 60, 55 and 45 respectively for the four sections, the over all average of marks per students is

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55.3

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52.25

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Solution

The correct option is D 52.25
Total number of students $= 40 + 35 + 45 + 42 = 162$
Total marks obtained
$= (40 \times 50) + (35 \times 60) + (45 \times 55) + (42 \times 45)$
$= 8465$
Overall average of marks per students $= \frac{8465}{162} = 52.25$

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55, 60

45

50, 55

60

Marks:	30 – 35	35 – 40	40 – 45	45 – 50	50 – 55	55 – 60	60 – 65
Frequency:	14	16	28	23	18	8	3

Marks obtained in a test by X standard students of two sections A and B are given below:

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No. of students in

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Determine: (i) Which section’s performance is better? And (ii) Which section’s performance is more variable?

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