DET–24 : PART–II (Mathematics & Science)
Questions 31–60
Q.31. A metallic solid cuboidal box of dimensions \(200\,\text{cm} \times 50\,\text{cm} \times 100\,\text{cm}\) is melted and recast into a solid cube. The difference between the surface areas of the two solids is:
- \(10000\text{ cm}^2\)
- \(25000\text{ cm}^2\)
- \(20000\text{ cm}^2\)
- \(15000\text{ cm}^2\)
Q.32. The mean of observations \(42, 48, x-15, x-17, x-20, 58, 60\) arranged in ascending order is \(53\). The median of the data is:
- 56
- 53
- 54
- 55
Q.33. The time spent by a student during a day is shown in a pie chart with central angles: School \(90^\circ\), Homework \(60^\circ\), Play \(60^\circ\), Sleep \(120^\circ\), Others \(30^\circ\). What is the difference between the time spent on sleep and school?
- 4 hours
- \(1\frac12\) hours
- 2 hours
- 3 hours
Q.34. A student was asked to find the value of \(x\) in \(x+4=3\). He subtracted \(4\) from \(3\). Which statement best describes this?
- Such problems should be avoided
- The student solved correctly
- The student made an algorithm-based error
- The student should memorize rules
Q.35. Which of the following mathematical statements is not true?
- Every multiple of a number is ≥ the number
- The number of factors of a number is finite
- Every factor is ≤ the number
- Every factor is always greater than the number
Q.36. The most appropriate way to introduce experimental probability to Class VIII is:
- Defining it on the board
- Tossing a fair coin repeatedly and noting outcomes
- Solving numerical problems
- Giving many theoretical examples
Q.37. Appropriate reasons for assessment at upper primary stage are:
(A) Identifying individual learner needs (B) Checking achievement of curriculum objectives (C) Verifying memorization of procedures (D) Selecting students for competitions
- (B) and (D)
- (A) and (C)
- (A), (C) and (D)
- (A) and (B)
Q.38. Which of the following is a closed-ended problem?
- Write four equivalent fractions of \(\frac{5}{7}\)
- List four rational numbers between \(\frac{5}{11}\) and \(\frac{10}{11}\)
- List four natural numbers between 104 and 109
- Write four integers less than 5
Q.39. A characteristic of an effective mathematics classroom is:
- Allowing multiple solution strategies
- Solving only teacher-given problems
- Emphasizing abstract nature only
- Encouraging individual work only
Q.40. While using questioning as an assessment tool, teachers should:
- Answer questions themselves
- Ask only low achievers
- Assess misconceptions and errors
- Ask many questions without pause
Q.41. If \((x+5)+7y = 5+(x+7y)\), which property of addition is used?
- Commutative & Associative
- Commutative
- Distributive
- Associative & Distributive
Q.42. The spiral approach recommended by NCF–2005 means:
- Revisiting concepts with increasing complexity
- Teaching new concepts each grade
- Repeating same content every year
- Teaching easy and hard topics together
Q.43. In which statement is the number \(6\) used in cardinal sense?
- 6 is successor of 5
- 6 is predecessor of 7
- She sat in the 6th row
- There are 6 elements in a set
Q.44. Evaluate: \[ \frac{0.125 \times 5^7 \times 8 \times 0.729}{0.017 \times 0.0081 \times 0.25} \]
- 153000
- 153
- 1530
- 15300
Q.45. If LCM of two numbers is 392, which cannot be their HCF?
- 196
- 28
- 42
- 56
Q.46. Smallest positive integer which is not a factor of \(264 \times 90 \times 1680\) is:
- 15
- 12
- 13
- 14
Q.47. If \[ \begin{array}{c} ABA \\ \times 5 \\ \hline 44B0 \end{array} \] then which is correct?
- A=8, B=9
- A=4, B=2
- A=9, B=8
- A=2, B=4
Q.48. If \(x\) is the smallest number subtracted from 7751 to make it a perfect square, find \(3x+5\).
- 16
- 7
- 10
- 13
Q.49. In \((5x+3y)(6x-5y)-(3x+7y)(4x+5y)\), the coefficient of \(xy\) is:
- 13
- 6
- 9
- 11
Q.50. One factor of \[ \frac{81x^2 - 126xy + 49y^2}{(5x-7y)^2} \] is:
- \(5x-7y\)
- \(7x-2y\)
- \(2x-5y\)
- \(7x+2y\)
Q.51. If \(\frac{7}{x}+\frac{1}{4}=\frac{1}{7}+\frac{2}{x}+\frac{1}{4}\), find \(\frac{5}{x}-\frac{3}{x}\).
- \(\frac{11}{8}\)
- 1
- \(\frac{3}{2}\)
- \(\frac{7}{5}\)
Q.52. Two articles sold at ₹348 each. Profit on A = 20%, loss on B = 13%. Overall profit (₹) is:
- 12
- 6
- 7
- 9
Q.53. ₹16000 amounts to ₹\(x\) in \(2\frac13\) years at 15% p.a. compounded yearly. Find \(x\).
- 22360
- 21160
- 21488
- 22218
Q.54. Difference of two complementary angles is \(40^\circ\). If smaller angle is \(y\), find \(2y+15^\circ\).
- 65°
- 45°
- 50°
- 55°
Q.55. Which figures do not have equal number of lines of symmetry?
- Kite & isosceles trapezium
- Isosceles triangle & kite
- Kite & parallelogram
- Rectangle & rhombus
Q.56. In triangle \(PQR\), point \(S\) lies on \(QR\) such that \(PS \perp QR\) and \(PS\) bisects \(\angle QPR\). Which is true?
- \(\triangle PQS \cong \triangle PRS\) (RHS)
- \(\triangle PQS \cong \triangle PSR\) (RHS)
- \(\triangle PQS \cong \triangle PRS\) (ASA)
- \(\triangle PQS \cong \triangle PSR\) (ASA)
Q.57. Which can be the third side of a triangle with sides 19 cm and 15 cm?
- 34 cm
- 3 cm
- 4 cm
- 33 cm
Q.58. In quadrilateral \(ABCD\): \(\angle A=(3x-10)^\circ,\ \angle B=(x+30)^\circ,\ \angle C=(2x+30)^\circ,\ \angle D=(2x-10)^\circ\). The quadrilateral is a:
- Rectangle
- Trapezium
- Parallelogram
- Kite
Q.59. Area of a triangle with sides 24 cm, 45 cm, 51 cm equals area of a rectangle of length 45 cm. Perimeter of rectangle is:
- 114 cm
- 55 cm
- 57 cm
- 110 cm
Q.60. From a circular sheet of diameter 16 cm, a circle of radius 6 cm is removed. Remaining area (use \(\pi=\frac{22}{7}\)) is:
- 44
- 176
- 88
- 66
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