Question

Persegi panjang abcd dengan panjang ab=2x-5 dan bc=x-10. jika kelilingnya 80 cm. tentukan:
-nilai x
-panjang & lebar
-keliling & luas

Answer 1

2 ( 2x - 5 + x - 10 ) = 80
2 ( 3x - 15 )            = 80
6x - 30                    = 80
6x                           = 110
  x                           = 18 1/3

Panjang = 31 2/3 cm
Lebar = 8 1/3 cm

Keliling = 80 cm
Luas = 263 8/9 cm²

Answer 2

- nilai x :
k= 2p + 2l = 80 cm
2 (2x-5) + 2 (x-10) = 80 cm
4x-5 + 2x-20 = 80 cm
4x+2x-5-20 = 80 cm
6x - 25 =80 cm
6x = 80 cm +25
6x = 105
x = 17,5
- panjang : 2x-5
= (2 x 17,5) -5
= 35 - 5
= 30 cm
- Lebar : x-10
= 17,5 - 10
= 7,5 cm
- keliling : 2p+2l
= (2x30 cm) + (2x7,5 cm)
= 60 cm + 15 cm
= 75 cm
- Luas : p x l
30 cm x 7,5 cm
225 cm