Find Volume With Fractional Edge Lengths
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6th Grade Math › Find Volume With Fractional Edge Lengths
A rectangular fish tank has a base area of $$4\frac{1}{2}$$ square feet and a height of $$1\frac{5}{6}$$ feet. If the tank is filled to $$\frac{3}{4}$$ of its total capacity, how many cubic feet of water are in the tank?
$$13\frac{3}{4}$$ cubic feet
$$11$$ cubic feet
$$6\frac{3}{16}$$ cubic feet
$$8\frac{1}{4}$$ cubic feet
Explanation
Convert to improper fractions: $$4\frac{1}{2} = \frac{9}{2}$$ and $$1\frac{5}{6} = \frac{11}{6}$$. Total volume = base area × height = $$\frac{9}{2} \times \frac{11}{6} = \frac{99}{12} = \frac{33}{4} = 8\frac{1}{4}$$ cubic feet. Water volume = $$\frac{3}{4} \times 8\frac{1}{4} = \frac{3}{4} \times \frac{33}{4} = \frac{99}{16} = 6\frac{3}{16}$$ cubic feet. Choice B gives the total tank volume. Choice C incorrectly adds dimensions. Choice D uses wrong fraction operations.
A rectangular prism has a volume of $$7\frac{1}{2}$$ cubic inches. If the length is $$2\frac{1}{2}$$ inches and the width is $$1\frac{1}{5}$$ inches, what is the height of the prism?
$$1\frac{1}{4}$$ inches
$$3\frac{1}{8}$$ inches
$$2\frac{1}{2}$$ inches
$$\frac{5}{2}$$ inches
Explanation
Convert to improper fractions: Volume = $$\frac{15}{2}$$, length = $$\frac{5}{2}$$, width = $$\frac{6}{5}$$. Using V = lwh: $$\frac{15}{2} = \frac{5}{2} \times \frac{6}{5} \times h$$. First find $$\frac{5}{2} \times \frac{6}{5} = \frac{30}{10} = 3$$. So $$\frac{15}{2} = 3h$$, which gives $$h = \frac{15}{2} \div 3 = \frac{15}{2} \times \frac{1}{3} = \frac{15}{6} = \frac{5}{2}$$ inches. Choice B repeats the length value. Choice C uses incorrect division. Choice D results from calculation errors.
Maria is building a concrete foundation that measures $$3\frac{1}{2}$$ yards long, $$2\frac{1}{4}$$ yards wide, and $$\frac{2}{3}$$ yards thick. Concrete costs $45 per cubic yard. What is the total cost of the concrete needed for this foundation?
$236.25
$315.00
$472.50
$525.00
Explanation
First convert mixed numbers: $$3\frac{1}{2} = \frac{7}{2}$$ and $$2\frac{1}{4} = \frac{9}{4}$$. Volume = $$\frac{7}{2} \times \frac{9}{4} \times \frac{2}{3} = \frac{7 \times 9 \times 2}{2 \times 4 \times 3} = \frac{126}{24} = \frac{21}{4} = 5.25$$ cubic yards. Cost = $$5.25 \times 45 = 236.25$$. Choice B uses incorrect conversion of mixed numbers. Choice C doubles the correct volume. Choice D uses wrong dimension calculations.
A rectangular prism has a base area of $12\tfrac{1}{2}\text{ cm}^2$ and a height of $\tfrac{4}{5}\text{ cm}$. What is the volume of the prism in cubic centimeters? (Use $V=bh$.)
$10\text{ cm}^3$
$16\text{ cm}^3$
$10\text{ cm}^2$
$13.3\text{ cm}^3$
Explanation
This question tests calculating the volume of rectangular prisms with fractional edge lengths using V=bh, base area times height, and understanding that packing with fractional unit cubes gives the same result. Base 12 1/2 cm²=25/2 cm², height 4/5 cm, V=(25/2)×(4/5)=(25×4)/(2×5)=100/10=10 cm³. If dimensions were known, V=lwh would match. Packing: suppose base fits certain cubes, but formula directly gives 10 cm³. Units cm³. Mistake like adding 12.5 + 0.8=13.3, or multiplying wrongly to 16. Calculate: (25/2)×(4/5)=10 cm³.
A rectangular prism has dimensions $\tfrac{3}{4}\text{ ft} \times 2\text{ ft} \times 1\tfrac{1}{2}\text{ ft}$. What is its volume in cubic feet?
$\tfrac{9}{4}\text{ ft}^3$
$\tfrac{9}{4}\text{ ft}$
$\tfrac{9}{8}\text{ ft}^3$
$\tfrac{17}{4}\text{ ft}^3$
Explanation
This question tests calculating the volume of rectangular prisms with fractional edge lengths using V=lwh, where you multiply the three edges, and understanding that packing with fractional unit cubes yields the same result. Dimensions: 3/4 ft × 2 ft × 1 1/2 ft (convert to 3/2 ft), so V=(3/4)×2×(3/2)=(3/4)×(3/2)×2=(9/8)×2=18/8=9/4 ft³. Or base (3/4)×2=3/2 ft², times height 3/2 ft = (3/2)×(3/2)=9/4 ft³. Packing with 1/4 ft cubes: along 3/4 fits 3, 2 fits 8, 3/2 fits 6, total 3×8×6=144 cubes each (1/4)³=1/64 ft³, 144×1/64=144/64=9/4 ft³. Units ft³. Error like adding fractions wrongly to 3/4 + 2 + 3/2 = 17/4. Steps: convert mixed to improper; multiply (3/4)×2×(3/2)=9/4.
A rectangular prism is filled by packing $\tfrac{1}{2}\text{ ft} \times \tfrac{1}{2}\text{ ft} \times \tfrac{1}{2}\text{ ft}$ unit cubes. The prism’s dimensions are $2\text{ ft} \times 1\text{ ft} \times \tfrac{1}{2}\text{ ft}$. How many of these $\tfrac{1}{2}$-foot cubes fit exactly in the prism?
2
4
6
8
Explanation
This question tests calculating the volume of rectangular prisms with fractional edge lengths using V=lwh (multiply three edges) or V=bh (base area times height), understanding packing with fractional unit cubes gives same result. Volume V=lwh: multiply length, width, height (2 ft × 3 ft × (1/2) ft = 2×3×0.5=3 ft³, fractional edges multiply like any numbers). Or V=bh: base area l×w times height (base 5×4=20 m², height 2.5 m, volume 20×2.5=50 m³). Packing: fill prism with unit cubes (if edge 1/2 ft, unit cube is (1/2)³=1/8 ft³, box 2×1×(1/2) holds 2÷(1/2)×1÷(1/2)×(1/2)÷(1/2)=4×2×1=8 cubes of 1/8 ft³ each, total 8×(1/8)=1 ft³—same as V=lwh). Units: cubic (ft³, cm³, in³—length unit cubed). For this prism, number of cubes: (2/(1/2)) × (1/(1/2)) × ((1/2)/(1/2)) = 4×2×1=8. Common errors include multiplying dimensions instead of dividing or miscounting fits.
A rectangular prism is $1\text{ ft}$ long, $\tfrac{1}{2}\text{ ft}$ wide, and $\tfrac{1}{2}\text{ ft}$ tall. If you pack it completely with cubes that each have edge length $\tfrac{1}{2}\text{ ft}$, how many such cubes fit inside?
1
2
4
8
Explanation
To calculate the volume of a rectangular prism with fractional edge lengths, use the formula V = l × w × h, where you multiply the three dimensions, or V = base area × height, and understand that packing the prism with fractional unit cubes yields the same result. For example, with dimensions 2 ft × 3 ft × (1/2) ft, V = 2 × 3 × 0.5 = 3 ft³; alternatively, using base area, if the base is 5 m × 4 m = 20 m² and height 2.5 m, then V = 20 × 2.5 = 50 m³; packing with 1/2 ft cubes in a 2 × 3 × (1/2) prism holds 4 × 6 × 1 = 24 cubes, each 1/8 ft³, totaling 3 ft³, with units always in cubic form like ft³ though here it's count. Another example: a prism 2 ft × 3 ft × (1/2) ft has V = 2 × 3 × (1/2) = 3 ft³; or 2.5 cm × 4 cm × 3 cm: V = 30 cm³; or base 6 × 5 = 30 cm², height 2.5 cm, V = 75 cm³. For this prism 1 ft × (1/2) ft × (1/2) ft packed with (1/2) ft cubes, along length 1/(1/2)=2, width (1/2)/(1/2)=1, height (1/2)/(1/2)=1, so 2 × 1 × 1 = 2 cubes. Common errors include thinking volume is 1 × 0.5 × 0.5 = 0.25 then dividing wrong to 1 or 8, confusing with cube volume $(1/2)^3$=1/8 then miscounting to 4, adding, or ignoring packing. To calculate packing, divide each dimension by cube edge: 1/(0.5)=2, etc., multiply counts 2×1×1=2; relates to V / cube volume = (0.25) / (0.125) = 2. Packing verifies formula; real for storage; avoid misdividing, confusing volume with count, adding, wrong units.
A small science container is shaped like a rectangular prism measuring $2.5\text{ cm} \times 4\text{ cm} \times 3\text{ cm}$. What is its volume?
$30\text{ cm}^2$
$9.5\text{ cm}^3$
$100\text{ cm}^3$
$30\text{ cm}^3$
Explanation
To calculate the volume of a rectangular prism with fractional edge lengths, use the formula V = l × w × h, where you multiply the three dimensions, or V = base area × height, and understand that packing the prism with fractional unit cubes yields the same result. For example, with dimensions 2 ft × 3 ft × (1/2) ft, V = 2 × 3 × 0.5 = 3 ft³; alternatively, using base area, if the base is 5 m × 4 m = 20 m² and height 2.5 m, then V = 20 × 2.5 = 50 m³; packing with 1/2 ft cubes in a 2 × 3 × (1/2) prism holds 4 × 6 × 1 = 24 cubes, each 1/8 ft³, totaling 3 ft³, with units always in cubic form like cm³. Another example: a prism 2 ft × 3 ft × (1/2) ft has V = 2 × 3 × (1/2) = 3 ft³; or 2.5 cm × 4 cm × 3 cm: V = 2.5 × 4 × 3 = 30 cm³; or base 6 × 5 = 30 cm², height 2.5 cm, V = 30 × 2.5 = 75 cm³. For this science container measuring 2.5 cm × 4 cm × 3 cm, the volume is 2.5 × 4 × 3 = 30 cm³. Common errors include adding dimensions like 2.5 + 4 + 3 = 9.5, forgetting cubic units to get 30 cm², mishandling decimals such as 2.5 × 4 = 100 incorrectly, using V = l + w + h, multiplying only two like 2.5 × 4 = 10 then forgetting 3, or errors like 2.5 × 4 = 1. For calculating, identify dimensions l=2.5, w=4, h=3, multiply as 2.5 × 4 = 10 then 10 × 3 = 30, and use cm³; mixed numbers convert to decimals like 1(1/2)=1.5 for multiplication. Base-height method: find base l × w, multiply by h; packing confirms formula; real uses include storage, aquariums, rooms; avoid adding, wrong units, fraction mishaps, missing dimensions, sum formulas.
A storage box is a rectangular prism with dimensions $2\text{ ft} \times 3\text{ ft} \times \tfrac{1}{2}\text{ ft}$. What is its volume in cubic feet? (Use $V=l\times w\times h$.)
$6\text{ ft}^3$
$5.5\text{ ft}^3$
$3\text{ ft}$
$3\text{ ft}^3$
Explanation
To calculate the volume of a rectangular prism with fractional edge lengths, use the formula V = l × w × h, where you multiply the three dimensions, or V = base area × height, and understand that packing the prism with fractional unit cubes yields the same result. For example, with dimensions 2 ft × 3 ft × (1/2) ft, V = 2 × 3 × 0.5 = 3 ft³; alternatively, using base area, if the base is 2 ft × 3 ft = 6 ft² and height 0.5 ft, then V = 6 × 0.5 = 3 ft³; packing with 1/2 ft cubes, the prism holds 4 along length, 6 along width, and 1 along height for 24 cubes, each 1/8 ft³, totaling 3 ft³, with units always in cubic form like ft³. Another example: a prism 2.5 cm × 4 cm × 3 cm has V = 2.5 × 4 × 3 = 30 cm³; or with base 6 cm × 5 cm = 30 cm² and height 2.5 cm, V = 30 × 2.5 = 75 cm³. For this storage box with dimensions 2 ft × 3 ft × (1/2) ft, the volume is 2 × 3 × 0.5 = 3 ft³. Common errors include adding dimensions like 2 + 3 + 0.5 = 5.5, forgetting cubic units to get 3 ft, mishandling fractions such as 2 × 3 ÷ 2 = 3 but sequenced wrong, using V = l + w + h, multiplying only two dimensions like 2 × 3 = 6, or decimal mistakes like treating 0.5 as 5. To calculate, identify the dimensions l=2, w=3, h=0.5, multiply step-by-step as 2 × 3 = 6 then 6 × 0.5 = 3, and add cubic units ft³; for mixed numbers, convert to improper fractions or decimals like 1(1/2) = 3/2 = 1.5 for easier multiplication. Using the base-height method, compute base area l × w then multiply by h; packing verifies the formula by showing the same volume; in real life, this applies to storage boxes for capacity, aquariums for water volume, or rooms for air space; avoid mistakes like adding instead of multiplying, omitting cubic units, fraction errors, forgetting the third dimension, or using sum formulas.
A rectangular prism has dimensions $\tfrac{3}{4}\text{ ft} \times 4\text{ ft} \times 2\text{ ft}$. What is the volume of the prism in cubic feet? (Use $V=lwh$.)
$\tfrac{3}{2}\text{ ft}^3$
$8\text{ ft}^3$
$6\text{ ft}^3$
$\tfrac{13}{4}\text{ ft}^3$
Explanation
This question tests calculating the volume of rectangular prisms with fractional edge lengths using V=lwh (multiply three edges) or V=bh (base area times height), understanding packing with fractional unit cubes gives same result. Volume V=lwh: multiply length, width, height (3/4 ft × 4 ft × 2 ft = (3/4)×4×2=6 ft³, fractional edges multiply like any numbers). Or V=bh: base area l×w times height (base 5×4=20 m², height 2.5 m, volume 20×2.5=50 m³). Packing: fill prism with unit cubes (if edge 1/2 ft, unit cube is (1/2)³=1/8 ft³, box 2×3×(1/2) holds 2÷(1/2)×3÷(1/2)×(1/2)÷(1/2)=4×6×1=24 cubes of 1/8 ft³ each, total 24×(1/8)=3 ft³—same as V=lwh). Units: cubic (ft³, cm³, in³—length unit cubed). For this prism, V=(3/4)×4×2=3×2=6 ft³. Common errors include improper fraction multiplication or adding dimensions.