1)
l=latimea
L=lungimea
perimetrul dreptunghiului=2l+2L sau (l+L)x2 sau l+l+L+L o folosim pe a doua
(l+L)x2=2008cm
L=3l
(l+3l)x2=2008cm
2l+6l=2008cm
8l=2008cm
l=2008:8
l=251
L=251x3
L=753
2)
1+3+5+7+.......+2013+2015=(2015+1)x(numarul de termeni):2
numarul de termeni=(2015-1):2+1=2014:2+1=1007+1=1008
(2015+1)x1008:2=2016x1008:2=2032128:2=1016064
1016064=1008x1008