1,6,11,16,21,26,31,36,41,46

1+6+11+16+21+26+31+36+41+46=235

a1=1,a2=6,a3=11,.......

a2-a1=a3-a2=........

a2-a1=d, d=6-1, d=5

a10=a1+9d, a10= 1+45=46

s10=10(1+46)/2=5.47=235

Otvet: 235

(sn=n(a1+an)/2)