Panjang = p = p cm

Lebar = l = 5 cm

Tinggi = t = 10 cm

Luas permukaan balok = 340 cm²

Luas permukaan balok

340 = $\left(2\times p\times l\right)+\left(2\times p\times t\right)+\left(2\times l\times t\right)$

340 = $\left(2\times p\times5\right)+\left(2\times p\times10\right)+\left(2\times5\times10\right)$

340 = 10p + 20p + 100

340 = 100 + 30p

340 - 100 = 30p

240 = 30p

p = $240\div30$ = 8 cm

Volume balok = $p\times l\times t$ = $8\times5\times10$ = 400 cm²