Question

Find the ${17}^{th}$ term from the end of the $AP:1,6,11,16,...201,216$.

Answer 1

$a=1,d=5$

Number of terms if last term is $216$.

$1+(n-1)\times 5=216$

$n-1=43$

$n=44$

${17}^{th}$ term from end $=44-17={27}^{th}$ term,

${27}^{th}$ term $=1+(27-1)\times 5=1+26\times 5=131$