luas permukaan balok :

(2 x p x l) + (2 x l x t) + (2 x p x t)

a. p 6cm l 3cm t 4cm

= (2 x 6 x 3) + (2 x 3 x 4) + (2 x 6 x 4)

= 36cm² + 24cm² + 48cm²

= 108cm²

b. p 7cm l 2cm t 3cm

= (2 x 7 x 2) + (2 x 2 x 3) + (2 x 7 x 3)

= 28cm² + 12cm² + 42cm²

= 82cm²

c. p 8cm l 4cm t 5cm

= (2 x 8 x 4) + (2 x 4 x 5) + (2 x 8 x 5).

= 64cm² + 40cm² + 80cm² .

= 184cm²

d. p 8cm l 7cm t 2cm

= (2 x 8 x 7) + (2 x 7 x 2) + (2 x 8 x 2)

= 112cm² + 28cm² + 32cm²

= 172cm²

cek lagi ya hitungan nya, takut ada yg salah