luas trapesium abcd =40. hitunglah keliling trapesium abcd

L = 40
(a + b)×t/2 = 40
(13 + 7) × t = 40 × 2
20t = 80
t = 80/20
t = 4 cm

cari panjang sisi kakinya
misalkan p
p^2 = 4^2 + ((13-7)/2)^2
p^2 = 4^2 + 3^2
p^2 = 16 + 9
p^2 = 25
p = akar25
p = 5 cm

Keliling = 2×5 + 7 + 13 = 10 + 20 = 30 cm