Question

Keliling suatu persegi panjang 78cm jika panjangnya dikurangi 3 dan kemudian dibagi 5 akan diperoleh lebar persegi panjang tersebut.Luas persegi panjang tersebut

Answer 1

K = 2 ( p + l)
78 = 2 ( p + l )
( 78 : 2 ) = p + l
39 = 33 + 6
p = 33 cm
l = 6 cm
L = p . l
L = 33 . 6
L = 198 cm2

Answer 2

K = 2(p+l)
l = (p - 3) : 5 

78 cm = 2(p + [(p - 3) : 5]
78 cm = 2p + 2(p/5 - 3/5)
78 cm = 10p/5 + 2p/5 - 6/5
78 cm = 12p/5 - 6/5
79,2 cm = 12p/5
396 cm = 12p
p = 396/12 = 33 cm
l = (33 - 3) : 5 = 6 cm

L = 33 X 6 = 198 cm²