Question 278426
{{{a[1]=17}}} {{{d=a[2]-a[1]=24-17=7}}}, {{{n=40}}} 
`
{{{S[n]=(n/2)(2a[1]+(n-1)*d)}}}
{{{S[40]=(40/2)(2*17+(40-1)*7)}}}
{{{S[40]=20(34+39*7)}}}
{{{S[40]=20(34+273)}}}
{{{S[40]=20(307)}}}
{{{S[40]=6140}}}
`
17+24+31+38+45+52+59+66+73+80+87+94+101+108+115+122+129+136+143+150
+157+164+171+178+185+192+199+206+213+220+227+234+241+248+255+262+269
+276+283+290 = 6140
`
Edwin