Differences in Volumes

V = LWH₂ - LWH₁=  (3.5)(2.5)(2.5) - (2.5)(1.5)(1.5)

= 21.875 - 5.625 = 16.25 in³ =   None of the above

$$V=\dfrac 1 3 L W H$$

Michelle's box is volume

$$V_{Michelle}\dfrac 1 3 (2.5)(1.5)(1.5)=1.875in^3$$

Cora's box is volume

$$V_{Cora}=\dfrac 1 3 (3.5)(2.5)(2.5)=7.292in^3$$

$$V_{Cora}-V_{Michelle}=7.292-1.875=5.417in^3$$

which doesn't seem to correspond with any of your choices.

Thanks Rom and Chris,

Rom, you made a little error I believe.

They are rectangular prisms NOT rectangular pyramids so the 1/3 should not be there.

Take out the 1/3 and Rom's answer is good.  

i got it off of a 6th grade CRT packet