Răspuns:
a)Pdreptunghi=l×2+L×2
Pdreptunghi =80cm
L=3•l
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Afla dimensiuni
80:2=40semiperimetru
l |---|
L|---|---|---| }40cm
40cm:4=10cm latimea
10×3=30cm lungimea
b)Pdreptunghi=L×2+l×2
Pdreptunghi=80cm
l=L:4
________________/___
Afla dimensiuni
80:2=40cmsemiperimetru
l |----|
L|----|----|----|----|}40cm
40:5=8cm latimea
8×4=32cm lungimea
c)Pdreptunghi=l×2+L×2
Pdreptunghi =80cm
L=l×7
______________/___
Afla dimensiuni
80:2=40semiperimetru
l |---|
L|---|---|---|---|---|---|---| }40
40:8=5cm latimea
5×7=35cm lungimea
d)Pdreptunghi=l×2+L×2
Pdreptunghi =80cm
L-l=20 cm
---------- ------/-----
Afla dimensiuni
80:2=40cm semiperimetru
l |--------|
L|--------|--20--| }40cm
40cm-20=20cm
20cm:2=10cm(latimea)
10cm+20cm=30cm(lungimea)
e)Pdreptunghi=l×2+L×2
Pdreptunghi =80cm
l=2/3 din Lungime
-----------------------------/--
Afla dimensiuni
80cm:2=40cm(semiperimetrul)
L |---|---|---|
l |---|---| }40cm
40cm:5=8cm
8cm×2=16cm latimea
8 cm×3=24 cm
