In a class, average height of all students is ‘a’ cms. Among them, average height of 10 students is ‘b’ cms and the average height of the remaining students is ‘c’ cms. Find the number of students in the class. (Here a > c and b > c )
Options:
A . $(a(b-c))/(a-c)$
B . $(b-c)/(a-c)$
C . $(b-c)/\text"10(a-c)"$
D . $\text"10(b-c)"/(a-c)$
Answer: Option D Answer: (d) Let the total number of students in the class be n. According to the question, an = 10 × b + (n – 10) c ⇒ an = 10b + nc – 10c ⇒ an – cn = 10b – 10c ⇒ n (a – c) = 10 (b – c) $⇒ n =\text"10 (b - c )"/ ( a - c )$
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