735
the multiple of 7 are 7, 14, 21, ...., 98 ( n = 14 )
this is an arithmetic sequence and the sum to n terms is
[tex]S_{n}[/tex] = [tex]\frac{n}{2}[/tex] [ 2a + (n - 1 )d ]
d = 14 - 7 = 21 - 14 = 7 and a = 7
[tex]S_{14}[/tex] = 7 [ ( 2 × 7 ) + (13 × 7 ) ] = 7 ( 14 + 91 ) = 735
