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Paper II, Part I. Answer all questions in this part. 1. A rectangular garden is 18.6 m long and 12.4 m. A student measured the length as 18.2 m and the width as 12.7 m. Find the percentage error in the: i. Measured length ii. Calculated perimeter iii. Calculated area

Mathematics

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Here are the solutions to the problems:

1. To find the percentage error, we use the formula:

Percentage Error=∣Measured Value−True Value∣True Value×100%\text{Percentage Error} = \frac{|\text{Measured Value} - \text{True Value}|}{\text{True Value}} \times 100\%

Given:
True length (LTL_T) = 18.6 m
True width (WTW_T) = 12.4 m
Measured length (LML_M) = 18.2 m
Measured width (WMW_M) = 12.7 m

  • i. Measured length
  1. Calculate the absolute error in length.

    $$
    \text{Error in length} = |L_M - L_T| = |18.2 - 18.6| = |-0.4| = 0.4 \text{ m}
    $$
    
  2. Calculate the percentage error in length.

    $$
    \text{Percentage Error (Length)} = \frac{0.4}{18.6} \times 100\% \approx 2.1505\%
    $$
    Rounded to two decimal places:
    $$
    \boxed{\text{2.15%}}
    $$
    
    • ii. Calculated perimeter
  3. Calculate the true perimeter and measured perimeter.

    $$
    P_T = 2(L_T + W_T) = 2(18.6 + 12.4) = 2(31.0) = 62.0 \text{ m}
    $$
    $$
    P_M = 2(L_M + W_M) = 2(18.2 + 12.7) = 2(30.9) = 61.8 \text{ m}
    $$
    
  4. Calculate the absolute error in perimeter.

    $$
    \text{Error in perimeter} = |P_M - P_T| = |61.8 - 62.0| = |-0.2| = 0.2 \text{ m}
    $$
    
  5. Calculate the percentage error in perimeter.

    $$
    \text{Percentage Error (Perimeter)} = \frac{0.2}{62.0} \times 100\% \approx 0.3226\%
    $$
    Rounded to two decimal places:
    $$
    \boxed{\text{0.32%}}
    $$
    
    • iii. Calculated area
  6. Calculate the true area and measured area.

    $$
    A_T = L_T \times W_T = 18.6 \times 12.4 = 230.64 \text{ m}^2
    $$
    $$
    A_M = L_M \times W_M = 18.2 \times 12.7 = 231.14 \text{ m}^2
    $$
    
  7. Calculate the absolute error in area.

    $$
    \text{Error in area} = |A_M - A_T| = |231.14 - 230.64| = 0.50 \text{ m}^2
    $$
    
  8. Calculate the percentage error in area.

    $$
    \text{Percentage Error (Area)} = \frac{0.50}{230.64} \times 100\% \approx 0.2168\%
    $$
    Rounded to two decimal places:
    $$
    \boxed{\text{0.22%}}
    $$
    

    2.

    • a) Let BB be the initial number of boys and GG be the initial number of girls.
  9. Set up equations based on the initial conditions.

    From the first sentence, "In a class of 45 students, the number of boys is three times the number of girls."
    $$
    B + G = 45 \quad (1)
    $$
    $$
    B = 3G \quad (2)
    $$
    
  10. Substitute equation (2) into equation (1) and solve for GG.

    $$
    3G + G = 45
    $$
    $$
    4G = 45
    $$
    $$
    G = \frac{45}{4} = 11.25
    $$
    
  11. Substitute the value of GG back into equation (2) to find BB.

    $$
    B = 3 \times 11.25 = 33.75
    $$
    Note: The number of students must be whole numbers. This problem as stated leads to non-integer values, indicating a potential flaw in the question's numerical values. However, based on the direct interpretation of the initial conditions, these are the calculated values.  
    Initial number of boys: $\boxed{\text{33.75}}$  
    Initial number of girls: $\boxed{\text{11.25}}$
    
    • b) Solve for xx in 72x−1=49x+27^{2x-1} = 49^{x+2}.
  12. Express both sides of the equation with the same base.

    $$
    7^{2x-1} = (7^2)^{x+2}
    $$
    $$
    7^{2x-1} = 7^{2(x+2)}
    $$
    
  13. Equate the exponents.

    $$
    2x-1 = 2(x+2)
    $$
    $$
    2x-1 = 2x+4
    $$
    
  14. Solve for xx.

    $$
    2x - 2x = 4 + 1
    $$
    $$
    0 = 5
    $$
    This is a contradiction, which means there is no value of $x$ that satisfies the equation.  
    The equation has $\boxed{\text{no solution}}$.
    

    3.

    • a) The volume of a cylinder is 1386 cm3^3. Its height is 14 cm. Find its radius. (Take π=227\pi = \frac{22}{7})
  15. Write down the formula for the volume of a cylinder.

    $$
    V = \pi r^2 h
    $$
    
  16. Substitute the given values into the formula.

    $$
    1386 = \frac{22}{7} \times r^2 \times 14
    $$
    
  17. Simplify and solve for r2r^2.

    $$
    1386 = 22 \times r^2 \times 2
    $$
    $$
    1386 = 44 r^2
    $$
    $$
    r^2 = \frac{1386}{44}
    $$
    $$
    r^2 = 31.5
    $$
    
  18. Solve for rr.

    $$
    r = \sqrt{31.5}
    $$
    $$
    r \approx 5.61248... \text{ cm}
    $$
    Rounded to two decimal places:
    $$
    r \approx \boxed{\text{5.61 cm}}
    $$
    
    • b) The 1st, 2nd and last terms of an Arithmetic Progression (A.P.) are 5, 11 and 59 respectively. Find the number of terms in the A.P.
  19. Identify the first term (a1a_1), second term (a2a_2), and last term (ana_n).

    $$
    a_1 = 5
    $$
    $$
    a_2 = 11
    $$
    $$
    a_n = 59
    $$
    
  20. Calculate the common difference (dd).

    $$
    d = a_2 - a_1 = 11 - 5 = 6
    $$
    
  21. Use the formula for the nn-th term of an A.P., an=a1+(n−1)da_n = a_1 + (n-1)d, to find nn.

    $$
    59 = 5 + (n-1)6
    $$
    
  22. Solve for nn.

    $$
    59 - 5 = (n-1)6
    $$
    $$
    54 = 6(n-1)
    $$
    $$
    \frac{54}{6} = n-1
    $$
    $$
    9 = n-1
    $$
    $$
    n = 9 + 1
    $$
    $$
    n = \boxed{\text{10}}
    $$
    

    4. Table 2.1 shows the distribution of ages (in years) of 60 people in a community.
    To calculate the mean age and standard deviation, we first find the midpoints (xix_i) for each age group and then calculate ∑fixi\sum f_i x_i and ∑fixi2\sum f_i x_i^2.

    Age (years)Midpoint (xix_i)Frequency (fif_i)fixif_i x_ixi2x_i^2fixi2f_i x_i^2
    10 - 20155752251125
    20 - 3025123006257500
    30 - 403515525122518375
    40 - 504514630202528350
    50 - 60559495302527225
    60 - 70655325422521125
    Total∑fi=60\sum f_i = 60∑fixi=2350\sum f_i x_i = 2350∑fixi2=103700\sum f_i x_i^2 = 103700
    • i. Mean age
  23. Use the formula for the mean of a grouped frequency distribution.

    $$
    \bar{x} = \frac{\sum f_i x_i}{\sum f_i}
    $$
    
  24. Substitute the calculated sums.

    $$
    \bar{x} = \frac{2350}{60} = \frac{235}{6}
    $$
    $$
    \bar{x} \approx 39.1666... \text{ years}
    $$
    Rounded to two decimal places:
    $$
    \bar{x} = \boxed{\text{39.17 years}}
    $$
    
    • ii. Standard deviation
  25. Use the formula for the standard deviation of a grouped frequency distribution.

    $$
    \sigma = \sqrt{\frac{\sum f_i x_i^2}{\sum f_i} - \left(\frac{\sum f_i x_i}{\sum f_i}\right)^2}
    $$
    
  26. Substitute the calculated sums.

    $$
    \sigma = \sqrt{\frac{103700}{60} - \left(\frac{2350}{60}\right)^2}
    $$
    
  27. Calculate the values inside the square root.

    $$
    \sigma = \sqrt{1728.3333... - (39.1666...)^2}
    $$
    $$
    \sigma = \sqrt{1728.3333... - 1533.9166...}
    $$
    $$
    \sigma = \sqrt{194.4166...}
    $$
    
  28. Calculate the square root.

    $$
    \sigma \approx 13.9433... \text{ years}
    $$
    Rounded to two decimal places:
    $$
    \sigma = \boxed{\text{13.94 years}}
    $$
    

    5.

    • a) Evaluate ∫02(3x2−2x+5)dx\int_{0}^{2} (3x^2 - 2x + 5) dx.
  29. Integrate the polynomial term by term.

    $$
    \int (3x^2 - 2x + 5) dx = \frac{3x^{2+1}}{2+1} - \frac{2x^{1+1}}{1+1} + 5x + C
    $$
    $$
    = \frac{3x^3}{3} - \frac{2x^2}{2} + 5x + C
    $$
    $$
    = x^3 - x^2 + 5x + C
    $$
    
  30. Evaluate the definite integral using the limits of integration.

    $$
    [x^3 - x^2 + 5x]_{0}^{2} = (2^3 - 2^2 + 5(2)) - (0^3 - 0^2 + 5(0))
    $$
    $$
    = (8 - 4 + 10) - (0)
    $$
    $$
    = 14 - 0
    $$
    $$
    = \boxed{\text{14}}
    $$
    
    • b) Solve for xx if log⁡(x+2)+log⁡(2x−1)=log⁡15\log(x+2) + \log(2x-1) = \log 15.
  31. Use the logarithm property log⁡A+log⁡B=log⁡(AB)\log A + \log B = \log (AB) to combine the terms on the left side.

    $$
    \log((x+2)(2x-1)) = \log 15
    $$
    
  32. Equate the arguments of the logarithms.

    $$
    (x+2)(2x-1) = 15
    $$
    
  33. Expand the left side and rearrange into a quadratic equation.

    $$
    2x^2 - x + 4x - 2 = 15
    $$
    $$
    2x^2 + 3x - 2 = 15
    $$
    $$
    2x^2 + 3x - 17 = 0
    $$
    
  34. Use the quadratic formula x=−b±b2−4ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} to solve for xx.

    $$
    x = \frac{-3 \pm \sqrt{3^2 - 4(2)(-17)}}{2(2)}
    $$
    $$
    x = \frac{-3 \pm \sqrt{9 + 136}}{4}
    $$
    $$
    x = \frac{-3 \pm \sqrt{145}}{4}
    $$
    
  35. Check for valid solutions.

    The arguments of the logarithms must be positive, so x+2>0  ⟹  x>−2x+2 > 0 \implies x > -2 and 2x−1>0  ⟹  x>0.52x-1 > 0 \implies x > 0.5. Thus, xx must be greater than 0.5. x1=−3+1454≈−3+12.044≈2.26 x_1 = \frac{-3 + \sqrt{145}}{4} \approx \frac{-3 + 12.04}{4} \approx 2.26 This solution is valid since 2.26>0.52.26 > 0.5. x2=−3−1454≈−3−12.044≈−3.76 x_2 = \frac{-3 - \sqrt{145}}{4} \approx \frac{-3 - 12.04}{4} \approx -3.76 This solution is not valid since −3.76≯0.5-3.76 \ngtr 0.5.
    Therefore, the only valid solution is: x=−3+1454 x = \boxed{\frac{-3 + \sqrt{145}}{4}}

    Handwritten Questions:

    • 2x+6=10\sqrt{2x+6} = 10
  36. Square both sides of the equation.

    $$
    (\sqrt{2x+6})^2 = 10^2
    $$
    $$
    2x+6 = 100
    $$
    
  37. Solve for xx.

    $$
    2x = 100 - 6
    $$
    $$
    2x = 94
    $$
    $$
    x = \frac{94}{2}
    $$
    $$
    x = \boxed{\text{47}}
    $$
    
    • 3x+1=4\sqrt{3x+1} = 4
  38. Square both sides of the equation.

    $$
    (\sqrt{3x+1})^2 = 4^2
    $$
    $$
    3x+1 = 16
    $$
    
  39. Solve for xx.

    $$
    3x = 16 - 1
    $$
    $$
    3x = 15
    $$
    $$
    x = \frac{15}{3}
    $$
    $$
    x = \boxed{\text{5}}
    $$
    
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