Question

heya...plss give full solution of given ques.

plss....its urgent☺

Answer 1

we have

a= 8

d= 4

an = 168

we know that

an= a+ (n-1)d

168= 8+(n-1)4

168= 8+4n-4
168= 4+4n
168 -4= 4n
164=4n
n= 164/4
n= 41


hence the total no. of members in the club is 41

Answer 2

Hello dear !!!

here youngest member's age is 'a'= 8 year
common difference = 4 month =4/12= 1/3year
sum of total age 'Sn' = 168 year !!

now we know that

Sn = n/2 {2a + (n-1)d }

Sn = n/2 {2×8 + (n-1)1/3}

168 = n/2 { 16 + n/3 - 1/3 }

168 = n/2 { 16 - 1/3 + n/3 )}

168 = n/2 {(48 - 1 + n/3 )}

168 = n/2 { 47 + n/3 )}

168 = 47n + n² /6

168×6 = n² + 47n

1008 = n² + 47n

0 = n² + 47n - 1008

0 = n² + 63n - 16n - 1008 {form of quadratic }

0 = n (n + 63) - 16 (n + 63)

0 = (n- 16) (n + 63)

hence , n - 16 = 0
n = 16

and , n + 63 = 0
n = - 63

(neglect - 63). then remaining is 16 hence 16 members are in that club ..

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Hope it helps you !!!

@Rajukumar111