Question

a) 4+8+12+16+...+204=

b) 2+4+6+...+102=

c) 2+4+6+...+20=2x(1+2+3+...+10)=

Answer 1

a) 4+8+12+16+...+204=
= 2×(1 + 2 + 3 + 4 +...+ 102) =
= 2 × 102 × 103 : 2 =
= 102 × 103 =
= 10 506

b) 2+4+6+...+102=
= 2 × ( 1 + 2 + 3 +...+ 51) =
= 2 × 51 × 52 : 2 =
= 51 × 52 =
= 2 652

c) 2+4+6+...+20=
= 2× (1 + 2 + 3 +...+ 10) =
= 2 × 10 × 11 : 2 =
= 10 × 11 =
= 110