Question

1.luas persegi panjang 280 cm².lebarnya 14 cm,berapa dm kelilingnya
2.keliling persegi panjang 60cm,lebarnya 12 cm,berapa luasnya
3.luas persegi 324 cm² .berapa kelilinya
4.keliling persegi 100 cm.berapa dm panjang rusuknya

Answer 1

1)
luas = 280 cm²
l = 14 cm = 1,4 dm
dit: keliling(dm)
luas = p × l
280 = p × 14
p = 280 : 14
p = 20 cm = 2 dm

keliling = 2p + 2l
keliling = 2(2) + 2(1,4)
keliling = 4 + 2,8
keliling = 6,8 dm


2)
keliling = 60 cm
lebar = 12cm
dit= luas?

keliling = 2p + 2l
60 = 2p + 2(12)
60 = 2p + 24
2p = 60-24
2p = 36
p = 18 cm

luas= p × l
luas = 18 × 12
luas = 216 cm²

3)
luas = 324 cm²
dit: keliling?
luas = S²
324 = S²
S = √324
S = 18 cm

keliling = 4S
keliling = 4 (18)
keliling = 72 cm

4)
keliling = 100 cm
dit= S(dm)?

keliling = 4S
100 = 4S
S = 100 : 4
S = 25 Cm
S = 2,5 dm

Answer 2

1. Lpp = pxl
280 = px14
280 = 14p
p = 20 cm
Kpp = 2(p+l)
Kpp = 2(20+14)
Kpp = 2x34
Kpp = 68 cm = 6,8 dm

2. Kpp = 2(p+l)
60 = 2(p+12)
60 = 2p +24
60-24 = 2p
36 = 2p
p = 18 cm
Lpp = pxl
Lpp = 18x12
Lpp = 216 cm

3. Lp = s²
324 = s²
s = √324
s = 18 cm
Kp = 4s
Kp = 18x4
Kp = 72

4. Kp = 4s
100 = 4s
s = 25 cm = 2,5 dm