nmr 18 cara cari t nya gmna ya?? nmr 15 tolong dibantu juga

15. perbandingan= 5 : 3 : 2
(5x3) : (3x3) : (2x3) = 15 : 9 : 6
Lpb = 2(pl+pt+lt) = 2(15x9+15x6+9x6)
=2(135+90+54) = 2x279 = 558 cm2

18. h = tinggi balok
lpb = 2(pl+pt+lt)
376 = 2 (10x8+10xh+8xh)
376 = 2(80+10h+8h) = 2(80+18h)
376 = 160 + 36h
376 -160 = 36h
216 = 36h
h = 216 : 36 = 6 cm
V = p x l x t = 10 x 8 x 6 = 480 cm3