Q11 of 48 Page 125

There are 40 students in a class, out of them 15 are boys. The mean of marks obtained by boys is 33 and that for girls is 35. Find out the mean of all students in the class.

We know that



⇒ Sum of observations = Mean ×Total number of observations


Mean of marks obtained by 15 boys = 33


⇒ Total marks obtained by boys = 33×15=495


Number of girls = 40 - 15=25


And Mean of marks obtained by 25 girls = 35


⇒ Total marks obtained by girls = 35×25=8755


Total marks obtained by class = Total marks obtained by boys and girls = 495 + 875 =1370



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