Respuesta :

find the volumes  og each  box

Single serving box = 1/2 * 7 *3 * 9 =  94.5  cm^3

Family size = 1/2 * 8 * 3 * 16 = 192 cm^3

Find the cost by unit volume:-  single costs 1.25 /  94.5 = 0.013228 
 family costs 2.5 / 192  0.01302

So the family bar costs less by unit volume  and is the better buy.