Math Problem Statement
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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:
(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:
Substituting cm:
(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) is a linear polynomial.
True (It is a linear polynomial of degree 1.)
(iii) (4, 0) is solution of .
True (Substitute and into the equation: , 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 .
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 .
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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
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