Jawabanmu

2014-05-19T15:08:26+07:00
L=((a+b)/2)xt
40=((8+2)/2)xt
40=5t
t=40/5
t=8 cm

Semoga membantu :)
2014-05-19T16:00:04+07:00
T = Luas trapesium : 1/2 X ( jumlah sisi sejajar ) 
= 40 cm : 1 /2 x ( 8 + 2 )
=40 : 5 = 8