We know each pizza has 8 slices and 10 persons will attend this party. If we consider a mean of 3 slices per person we'll need a total of 30 slices (10x3=30), now we divide these 30 slices between the 8 slices we haver per pizza in order to have the number of pizzas needed.
<em>Since we can't order 3.75 pizzas we round this number to 4, this way we will have 32 slices. (4x8=32)</em>
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