Cristinikaask
a fost răspuns

Calculati cat mai rapid:
a) 10+20+30+40+...+90=
b) 100+200+300+...+1000=
c) 2222+4444+6666+8888=
d) 11111+22222+33333+...+99999

Răspuns :

Miky93ask
a)10+20+...+90= (10+90)*9/2=  100*9/2= 50*9=450

b)100+200+...+1000= (10+1000)*10/2= 1100*5= 5500

c)2222+8888+4444+6666= 11110 + 11110= 22220

d)(11111+99999)*9/2=  111 110 *9/2=  55555*9= 499 995