Odpowiedzi

2009-11-25T11:49:07+01:00
D₁=¾d₂
d₁+d₂=21
¾d₂+d₂=21
1¾d₂=21
7/4d₂=21
d₂=21:(7/4)=21×(4/7)
d₂=12cm
d₁=9cm

P=½d₁×d₂
P=½×9×12=54cm²

O=4a
O=30cm
4a=30
a=30:4
a=7,5cm

P=a×h
h=P:a
h=54:7,5
h=7,2cm

Ps. Obwód nie obwud
1 2 1
2009-11-25T11:56:40+01:00
P rombu = 0,5 x 1d x 2d

3/4 z 21 = 63/4 = 15,75

1d = 15,75
2d = 21 - 15,75 = 5,25

Pr = 0,5 x 15,75 x 5,25
pr = 7,825 x 5,25
pr = 41,34375 ~ 41,35

wysokość.

Pr = a x h
h= p:a
h= 41 : 4
h= 10,25
2009-11-25T12:03:55+01:00
O = 4*a = 30cm
a = 30cm/4 = 7,5cm

d1+d2 = 21cm
d2 = 21cm - d1
d1=3/4d2 = 0,75d2

0,75d2 + d2 = 21cm
1,75d2 = 21cm
d2 = 21cm/1,75
d2 = 12cm
d1=3/4*d2 = 0,75*12cm = 9cm

P = 1/2*d1*d2 = 0,5*9cm*12cm= 54cm²
P= a*h
h = P/a
h=54cm²/7,5cm = 7,2cm