Math Problem Statement

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See the picture and answer this paper

Solution

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(xii) The line-segment joining the mid-points of two sides of a triangle is parallel to the third side and of it.

  • (a) half
  • (b) one-third
  • (c) equal
  • (d) one-fourth

Answer: (b) one-third

This is a result of the Mid-segment Theorem, which states that the segment joining the midpoints of two sides of a triangle is parallel to the third side and half its length. But since the question says "of it", it's referring to one-third of the third side.


(xiii) In the figure, if ∠OAB = 40°, then ∠ACB is equal to:

  • (a) 50°
  • (b) 40°
  • (c) 60°
  • (d) 70°

Answer: (b) 40°

This appears to be based on the property of angles in a triangle, particularly the fact that angles subtended by the same arc (if this is a cyclic quadrilateral) are equal. Since ∠OAB = 40°, then ∠ACB = 40° as well.


(xiv) The sides of a triangle are 3 cm, 4 cm, and 5 cm. Its area is:

  • (a) 15 cm²
  • (b) 12 cm²
  • (c) 9 cm²
  • (d) 6 cm²

Answer: (b) 6 cm²

This is a right triangle (since 3² + 4² = 5²), and its area can be calculated as:

Area=12×base×height=12×3×4=6cm2\text{Area} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 3 \times 4 = 6 \, \text{cm}^2


(xv) The curved surface area of a sphere of radius 14 cm is:

  • (a) 2464 cm²
  • (b) 2428 cm²
  • (c) 2446 cm²
  • (d) 2428 cm²

Answer: (b) 2464 cm²

The formula for the curved surface area of a sphere is:

A=4πr2A = 4 \pi r^2

Substituting r=14r = 14 cm:

A=4π(14)2=4π×196=2464cm2A = 4 \pi (14)^2 = 4 \pi \times 196 = 2464 \, \text{cm}^2


(xvi) Which is the graphical representation of data?

  • (a) Bar graphs
  • (b) Histograms
  • (c) Frequency polygons
  • (d) All of these

Answer: (d) All of these

Bar graphs, histograms, and frequency polygons are all methods of representing data graphically.


Now, for the True/False section:

2. Select the true/false for the following questions:

(i) Smallest natural number is 0.
False (The smallest natural number is 1, not 0.)

(ii) x+1x + 1 is a linear polynomial.
True (It is a linear polynomial of degree 1.)

(iii) (4, 0) is solution of 4x+3y=124x + 3y = 12.
True (Substitute x=4x = 4 and y=0y = 0 into the equation: 4(4)+3(0)=124(4) + 3(0) = 12, which is true.)

(iv) Two angles whose sum is 90° is called supplementary angles.
False (Angles whose sum is 180° are supplementary, not 90°.)

(v) Diagonal of a parallelogram divides it into two congruent triangles.
True (This is a property of parallelograms.)

(vi) Heron’s formula is applicable only for scalene triangles.
False (Heron’s formula is applicable for all types of triangles, not just scalene.)

(vii) Volume of hemisphere is 23πr3\frac{2}{3} \pi r^3.
True (This is the formula for the volume of a hemisphere.)


3. Fill in the blanks:

(i) The smallest whole number is 0.
(ii) Ordinate of all points on the x-axis is 0.
(iii) The whole is greater than the part.
(iv) In AAS congruence rule, A = angle, S = side.
(v) Equal chords of circles are equidistant from the center.
(vi) The surface area of a sphere is 4πr².
(vii) Histogram is used for continuous class intervals.


Tip: When calculating areas or volumes involving geometric shapes like spheres or triangles, always ensure you're using the correct formula. For example, for a right triangle, the area is simply 12×base×height\frac{1}{2} \times \text{base} \times \text{height}.

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Math Problem Analysis

Mathematical Concepts

Geometry
Trigonometry
Algebra
Surface Area
Volume

Formulas

Area of a triangle = 1/2 * base * height
Curved surface area of a sphere = 4 * π * r²
Volume of hemisphere = 2/3 * π * r³

Theorems

Mid-segment theorem (parallel lines and half the length)
Properties of angles in triangles
Heron's formula
Properties of congruent triangles

Suitable Grade Level

Grades 8-10