Question

12 +2 +32 +4² + .........+ 102 = 385, then find 2? +4 +6 +....... +20' ?
1) 770
2) 1540 3) 1115 4) 385 5) None​

Answer 1

Answer:

no. of terms=(tn-ti)/d+I=(20-2)/2+l

=IO

S10=n/2{2a+(n-1)d}

= 10/2{2x2+(10-1) 2 }

= 5(4+18) = 110