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Pule has 3 identical cuboids, each has length / cm and width w cm. The distance around the base of this shape is given by an equation 61 + 2w = 72, while the area of the base of the shape is given by an equation 3lw = 243.

Mathematics

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Answer

b

27 cm or 9 cm\text{27 cm or 9 cm}

9 cm\text{9 cm}

324 cm3\text{324 cm}^3

Step-by-step solution

4 steps

Part a

Pule has 3 identical cuboids, each with length ll cm and width ww cm. They are placed together to form a larger shape.

The distance around the base of this shape (perimeter) is given by 6l+2w=726l + 2w = 72.
The area of the base of this shape is given by 3lw=2433lw = 243.

Part b

27 cm or 9 cm\text{27 cm or 9 cm}

  1. Form an equation in ww (Part b(i)).

    The perimeter of the combined base is 2(3l+w)2(3l + w).

    2(3l+w)=722(3l + w) = 72

    Divide by 2:

    3l+w=363l + w = 36

    Express 3l3l in terms of ww:

    3l=36−w3l = 36 - w

    The area of the combined base is (3l)w(3l)w.

    (3l)w=243(3l)w = 243

    Substitute the expression for 3l3l into the area equation:

    (36−w)w=243(36 - w)w = 243 36w−w2=24336w - w^2 = 243

    Rearrange the terms to form a quadratic equation in standard form:

    w2−36w+243=0w^2 - 36w + 243 = 0
  2. Solve the equation for ww (Part b(ii)).

    The equation is w2−36w+243=0w^2 - 36w + 243 = 0.
    We need to find two numbers that multiply to 243 and add up to −36-36. These numbers are −9-9 and −27-27.

    w2−27w−9w+243=0w^2 - 27w - 9w + 243 = 0

    Factor by grouping:

    w(w−27)−9(w−27)=0w(w - 27) - 9(w - 27) = 0 (w−27)(w−9)=0(w - 27)(w - 9) = 0

    Set each factor to zero to find the possible values for ww:

    w−27=0  ⟹  w=27w - 27 = 0 \implies w = 27 w−9=0  ⟹  w=9w - 9 = 0 \implies w = 9

    The possible values for ww are 27 cm or 9 cm\boxed{\text{27 cm or 9 cm}}.

  3. Find the length of the cuboid (Part b(iii)).

    We use the relation 3l=36−w3l = 36 - w.
    Case 1: If w=9w = 9 cm

    3l=36−93l = 36 - 9 3l=273l = 27 l=273=9 cml = \frac{27}{3} = 9 \text{ cm}

    In this case, the dimensions of each cuboid's base are l=9l=9 cm and w=9w=9 cm. The combined shape's base would be 3l×w=3(9)×9=27×93l \times w = 3(9) \times 9 = 27 \times 9 cm. This is consistent with the diagram showing a shape longer than it is wide.

    Case 2: If w=27w = 27 cm

    3l=36−273l = 36 - 27 3l=93l = 9 l=93=3 cml = \frac{9}{3} = 3 \text{ cm}

    In this case, the dimensions of each cuboid's base are l=3l=3 cm and w=27w=27 cm. The combined shape's base would be 3l×w=3(3)×27=9×273l \times w = 3(3) \times 27 = 9 \times 27 cm. This would mean the combined shape is wider than it is long, which contradicts the visual representation in the diagram.

    Therefore, we choose the dimensions that are consistent with the diagram. The length of the cuboid is l=9l=9 cm.
    The length of the cuboid is 9 cm\boxed{\text{9 cm}}.

  4. Calculate the volume of each cuboid (Part b(iv)).

    The height of the cuboid is given as h=4h = 4 cm.
    Using the dimensions l=9l=9 cm and w=9w=9 cm.
    The volume of one cuboid is given by the formula V=l×w×hV = l \times w \times h.

    V=9 cm×9 cm×4 cmV = 9 \text{ cm} \times 9 \text{ cm} \times 4 \text{ cm} V=81 cm2×4 cmV = 81 \text{ cm}^2 \times 4 \text{ cm} V=324 cm3V = 324 \text{ cm}^3

    The volume of each cuboid is 324 cm3\boxed{\text{324 cm}^3}.

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