The volume of a rectangular prism is (length) x (width) x (height).
The volume of the big one is (2.25) x (1.5) x (1.5) = 5.0625 cubic inches.
The volume of the little one is (0.25)x(0.25)x(0.25)= 0.015625 cubic inch
The number of little ones needed to fill the big one is
(Volume of the big one) divided by (volume of the little one) .
5.0625 / 0.015625 = 324 tiny cubies
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Doing it with fractions instead of decimals:
The volume of a rectangular prism is (length) x (width) x (height).
Dimensions of the big one are:
2-1/4 = 9/4
1-1/2 = 3/2
1-1/2 = 3/2
Volume = (9/4) x (3/2) x (3/2) =
(9 x 3 x 3) / (4 x 2 x 2) =
81 / 16 cubic inches.
As a mixed number: 81/16 = 5-1/16 cubic inches
Volume of the tiny cubie = (1/4) x (1/4) x (1/4) = 1/64 cubic inch.
The number of little ones needed to fill the big one is
(Volume of the big one) divided by (volume of the little one) .
(81/16) divided by (1/64) =
(81/16) times (64/1) =
5,184/16 = 324 tiny cubies.