` a=5,d=3 ` और ` a_nn =50 ` दिया है| n और `S_n` ज्ञात कीजिए| एक `A.P. `में,

Explanation

` " " a=5 ,d =3 ,a_n =50`
` rArr a+(n -1) d=50`
` rArr 5+ (n-1) 3=50 " " rArr (n-1) 3 =45`
` rArr " " n-1 =15 " " rArr " " n=16`
अब ` " " S_n =(n)/(2) [2a +(n-1) d]`
` " " (16)/(2) [2xx5 +(16-1) xx3]`
` " "=8 (10+45 ) =8 xx55 =440 `
` therefore " " n=16` और ` `S_n =440`