Limas T.ABCD

Lp = 1360 cm^2

sa = 20 cm

LsABT = LsBCT = LsCDT = LsADT

AT = BT = CT = DT

LsABT

= 1/4 × (Lp - La)

= 1/4 × (Lp - (sa × sa))

= 1/4 × (1360 - (20 × 20))

= 1/4 × (1360 - 400)

= 1/4 × 960

= 240 cm^2

LsABT = 1/2 × sa × t

240 = 1/2 × 20 × t

240 = 10 × t

t = 240/10

t = 24 cm

panjang rusuk tegak limas (AT)

= V(t^2 + (1/2 × sa)^2)

= V(24^2 + (1/2 × 20)^2)

= V(24^2 + 10^2)

= V(576 + 100)

= V676

= 26 cm

keterangan :

Lp = luas permukaan limas

sa = ukuran sisi alas limas

LsABT = Luas segitiga ABT (luas salah satu sisi tegak limas)

t = tinggi segitiga ABT

V = akar

panjang rusuk tegak limas = AT , BT , CT , DT