bantuin dong 27 28 pakek cara

27 . Luas persegi panjang = p x l = pl
       panjang baru = p + 20%p = p + 0,2p
       lebar baru = l - 20%l = l - 0,2l
       Luas persegi panjang baru = (p + 0,2p) x (l - 0,2l)
                                                   = pl + 0,2pl - 0,2pl - 0,04pl
                                                   = pl - 0,04pl
                                                   = 0,96 pl
       Selisih Luas = 0,96pl - pl = - 0,04 pl = - 4% pl
       Jadi LUas persegi panjang tersebut turun 4% (Jawaban B)

28. Kelilling alas = 2[tex] \pi [/tex]r
      2[tex] \pi [/tex]r = 6[tex] \pi [/tex]
      r = 3 cm

      Volume = [tex] \pi [/tex] . r² . t
      99 [tex] \pi [/tex] = [tex] \pi [/tex] . 3² . t
      99 [tex] \pi [/tex] = 9 [tex] \pi [/tex] t
      t = 99 [tex] \pi [/tex] / 9 [tex] \pi [/tex]
      t = 11 cm
      Jawaban D

27) Luas = p . l
p meningkat 20% => (100 + 20)%p = 120%p
l berkurang 20% => (100 - 20)% l = 80% l
Luas = 120% p . 80% l
= 120/100 . 80/100 . p . l
= 96/100 p . l
= 96% p . l
Artinya turun berkurang (100 - 96) % = 4%

28) keliling alas = 6π
2πr = 6π
r = 3

Vsilinder = 99π
π r^2 t = 99π
r^2 . t = 99
(3^2) . t = 99
9t = 99
t = 11 cm