Question

Calculati;
a)1+2+3+4+.....+22=
b)2+4+6+8.....+44=
c)5+10+15+20+....+110=
d)10+20+30+40+....+220=

Answer 1

Vom aplica formula nx(n+1)/2 n fiind numarul 22
a)22x(22+1)/2=11x23=253
b)44x(44+1)/2=22x45=990
c)110x(110+1)=55x111=6105
d)220x(220+1)/2=110x221=24310

Answer 2

a) (22×23)÷2=11×23=253
b) 2×(1+2+3+...+22)=2×(22×23)÷2=22×23=506
c) 5×(1+2+3+...+22)=5×(22×23)÷2=5×11×23=1265
d) 10×(1+2+3+...+22)=10×(22×23)÷2=10×11×23=
=2530