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A rectangular mat has an area of 216 cm2. The width of the mat is 6 cm shorter than the length. Find the width of the mat.

Mathematics

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Step-by-step solution

10 steps
  1. Define variables for the dimensions of the mat.

    Let LL be the length of the mat and WW be the width of the mat.

  2. Write down the given information as equations.

    The area of the rectangular mat is 216 cm2216 \text{ cm}^2. The formula for the area of a rectangle is A=L×WA = L \times W.

    L×W=216(1)L \times W = 216 \quad (1)

    The width of the mat is 6 cm6 \text{ cm} shorter than the length.

    W=L−6(2)W = L - 6 \quad (2)
  3. Substitute equation (2) into equation (1) to form a quadratic equation.

    L(L−6)=216L(L - 6) = 216 L2−6L=216L^2 - 6L = 216 L2−6L−216=0L^2 - 6L - 216 = 0
  4. Solve the quadratic equation for LL.

    We can factor the quadratic equation. We need two numbers that multiply to −216-216 and add to −6-6. These numbers are 12 and −18-18.

    (L+12)(L−18)=0(L + 12)(L - 18) = 0

    This gives two possible values for LL:

    L=−12orL=18L = -12 \quad \text{or} \quad L = 18

    Since length cannot be negative, we take L=18 cmL = 18 \text{ cm}.

  5. Calculate the width WW using the value of LL.

    Substitute L=18L = 18 into equation (2):

    W=18−6W = 18 - 6 W=12 cmW = 12 \text{ cm}

    The width of the mat is 12 cm\boxed{\text{12 cm}}.

  6. Define variables for the present ages.

    Let MM be the mother's present age and DD be the daughter's present age.

  7. Write down the given information as equations.

    A mother is five times as old as her daughter.

    M=5D(1)M = 5D \quad (1)

    Six years ago, their ages were M−6M-6 and D−6D-6. The product of their ages was 68.

    (M−6)(D−6)=68(2)(M - 6)(D - 6) = 68 \quad (2)
  8. Substitute equation (1) into equation (2) to form a quadratic equation in terms of DD.

    (5D−6)(D−6)=68(5D - 6)(D - 6) = 68

    Expand the equation:

    5D2−30D−6D+36=685D^2 - 30D - 6D + 36 = 68 5D2−36D+36−68=05D^2 - 36D + 36 - 68 = 0 5D2−36D−32=05D^2 - 36D - 32 = 0
  9. Solve the quadratic equation for DD using the quadratic formula D=−b±b2−4ac2aD = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}.

    Here, a=5a = 5, b=−36b = -36, c=−32c = -32.

    D=−(−36)±(−36)2−4(5)(−32)2(5)D = \frac{-(-36) \pm \sqrt{(-36)^2 - 4(5)(-32)}}{2(5)} D=36±1296+64010D = \frac{36 \pm \sqrt{1296 + 640}}{10} D=36±193610D = \frac{36 \pm \sqrt{1936}}{10} D=36±4410D = \frac{36 \pm 44}{10}

    This gives two possible values for DD:

    D1=36+4410=8010=8D_1 = \frac{36 + 44}{10} = \frac{80}{10} = 8 D2=36−4410=−810=−0.8D_2 = \frac{36 - 44}{10} = \frac{-8}{10} = -0.8

    Since age cannot be negative, the daughter's present age is D=8D = 8 years.

  10. Calculate the mother's present age MM using the value of DD.

    Substitute D=8D = 8 into equation (1):

    M=5×8M = 5 \times 8 M=40 yearsM = 40 \text{ years}

    The mother's present age is 40 years\boxed{\text{40 years}} and the daughter's present age is 8 years\boxed{\text{8 years}}.

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