Question

Cine face asta are 45 de puncte.

Answer 1

3.
a)
P=4×1,2=4,8 cm
A=(1,2)^2=1,44 cm^2
b)
P=4L=72 =>L=18 cm
A=18^2=324 cm^2
c)
A=L^2=36 =>L=6 cm
P=4×6=24 cm

4.
V=L×l×h
L=120 cm=12 dm
l=11 dm
h=1 m=10 dm
V=1320 dm^3 sau litri

2.
a)
l=25/5=5 cm
P=2L+2l=50+10=60 cm
A=L×l=125 cm^2
b)
L×5=40 =>L=8 cm
P=2×8+2×5=26 cm
c)
P=2×17+2×l=72 sau 17+l=36 => l=19 cm
A=17×19=323 cm^2
d)
P=2L+2l=24 =>L+l=12
L=2l
2l+l=12
3l=12 =>l=4 cm și L=8 cm
A=4×8=32 cm^2

Answer 2

2) ABCD→ dreptunghi

a)  L = 25 cm;  l = 1 / 5 din L = 25 / 5 = 5 cm ( latimea)

P = 2 x ( L + l ) = 2 x ( 25 cm + 5 cm ) = 2 x 30 cm = 60 cm → perimetrul

A = L x l = 25 cm x 5 cm = 125 cm² → aria

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b)  A = 40 cm;  l = 5 cm

A = L x l = 40

L x 5 cm = 40 cm ⇒  L = 40 : 5 ⇒  L = 8 cm → lungimea

P = 2 x ( L + l ) = 2 x ( 8 cm + 5 cm ) = 2 x 13 cm = 26 cm

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c)  P = 72 cm;  l  = 17  ( este latimea dreptunghiului si NU latimea)

72 cm : 2 = 36 cm  → semiperimetrul = suma dintre L si latime

L + l = 36 cm

L + 17 cm  = 36 cm ⇒   36 cm - 17 cm = 19 cm → lungimea ( L )

Aria = L x l = 19 cm x 17 cm = 323 cm²

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d)   P = 24 cm;  l = L : 2 ⇒  L = 2 × l

L + l = 24 cm : 2

2 × l + l = 12 cm → semiperimetrul

3 × l = 12 cm ⇒   l = 12 cm : 3 = 4 cm ( latimea)

L = 2 × 4 cm = 8 cm ( lungimea)

Aria = L x l = 8 cm x 4 cm = 32 cm²

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3)  ABCD → patrat

a)   latura ( l ) = 1,2 cm

P = 4 x 1,2 cm = 4,8 cm

Aria = 1,2 cm x 1,2 cm = 1,44 cm

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b)    P = 72 mm;  

latura = 72 mm : 4 = 18 mm

Aria = 18 mm x 18 mm = 324 mm²

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c)  A = 36 cm²

latura = √36 cm² = 6 cm

Perimetrul = 4 x 6 cm = 24 cm

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4) paralelipiped

L = 120 cm = 12 dm ; h = 1 m = 10 dm si l = 11 dm

Volumul = L x h x l = 12 dm x 10 dm x 11 dm = 1 320 dm³