ICSE Class X Prelims 2025 : Mathematics (Bombay Scottish School, Mahim, Mumbai) |
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b) ΔPCA
Reasoning:
1. Given: PQ || BC, AB || QR, and PC intersects QR at O.
2. Since PQ || BC, ΔPQC is similar to ΔABC (by the angle-angle similarity criterion).
3. AB || QR implies that ∠BAC = ∠QCA (alternate angles).
4. In ΔPBC and ΔPCA:
- ∠BPC is common
- ∠PBC = ∠PCA (since PQ || BC, these are corresponding angles)
- ∠PCB = ∠BAC = ∠QCA (from steps 2 and 3)
5. By the angle-angle similarity criterion, ΔPBC is similar to ΔPCA.
Therefore, the correct answer is ΔPCA.
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ICSE Class X Prelims 2025 : Mathematics (Bombay Scottish School, Mahim, Mumbai) |
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d) (II) and (III)
Reasoning:
In a rhombus:
1. The diagonals bisect each other at right angles.
2. The diagonals bisect the angles of the rhombus.
3. The diagonals are the perpendicular bisectors of each other.
Given these properties:
I. The bisector of ∠A and ∠C is not necessarily equidistant from A and C. It's only true for the diagonal that bisects these angles.
II. The perpendicular bisector of AC is equidistant from A and C by definition.
III. The diagonal BD is perpendicular to and bisects AC, so it is equidistant from A and C.
Therefore, statements II and III are correct.
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ICSE Class X Prelims 2025 : Mathematics (Bombay Scottish School, Mahim, Mumbai) |
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b) (p+q)/2
Reasoning:
1. In an arithmetic progression, the middle term between any two terms is their average.
2. Here, we have:
(x+y)th term = p
(x-y)th term = q
We need to find the xth term.
3. The xth term is exactly in the middle of the (x+y)th and (x-y)th terms.
4. Therefore, the xth term will be the average of p and q:
xth term = (p + q) / 2
Thus, the correct answer is (p+q)/2.
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ICSE Class X Prelims 2025 : Mathematics (Bombay Scottish School, Mahim, Mumbai) |
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a) y = 2
Reasoning:
1. When a point is reflected over a horizontal line y = k, its x-coordinate remains the same, and its y-coordinate changes to 2k - y.
2. Here, the line of reflection is y = 3, so k = 3.
3. The original point P is (3, 4).
4. After reflection:
x-coordinate of P' = 3 (unchanged)
y-coordinate of P' = 2(3) - 4 = 2
5. So, P' is (3, 2).
6. A line parallel to the x-axis passing through P' would have the equation y = 2.
Therefore, the equation of the line passing through P' parallel to the x-axis is y = 2.
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ICSE Class X Prelims 2025 : Mathematics (Bombay Scottish School, Mahim, Mumbai) |
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a) A is true, R is false.
Reasoning:
Assertion (A) is true: In ΔPQA, sin A is indeed greatest for this triangle arrangement. This is because sin A is opposite/hypotenuse, and PQ (opposite to angle A) is the longest side in this right-angled triangle.
Reason (R) is false: The value of sin A does depend on the side lengths. It is specifically the ratio of the opposite side to the hypotenuse. While it's true that sin A is a ratio, this ratio is directly related to the lengths of the sides.
Therefore, A is true, but R is false.
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ICSE Class X Prelims 2025 : Mathematics (Bombay Scottish School, Mahim, Mumbai) |
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c) 3cm
Reasoning: For a right-angled triangle that circumscribes a circle:
1. Let r be the radius of the inscribed circle.
2. In a right-angled triangle, if a and b are the lengths of the two shorter sides, and c is the hypotenuse, then:
r = (a + b - c) / 2
3. We know AB = 15cm, AC = 17cm. Let's find BC using the Pythagorean theorem:
BC² = AC² - AB² = 17² - 15² = 289 - 225 = 64
BC = 8cm
4. Now we can apply the formula:
r = (15 + 8 - 17) / 2 = 6 / 2 = 3cm
Therefore, the radius of the inscribed circle is 3cm.
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ICSE Class X Prelims 2025 : Mathematics (Bombay Scottish School, Mahim, Mumbai) |
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b) 115°
Reasoning: In the diagram:
1. APB and AQB are angles in a semicircle, so they are right angles (90°).
2. ΔAPB is isosceles (AP = PB as they are radii), so ∠PAB = ∠PBA.
3. Given that ∠APB = 130°, we can find ∠PAB:
∠PAB + ∠APB + ∠PBA = 180° (sum of angles in a triangle)
∠PAB + 130° + ∠PAB = 180°
2∠PAB = 50°
∠PAB = 25°
4. In ΔACD:
∠CAD + x + 25° = 180° (sum of angles in a triangle)
x = 180° - 25° - ∠CAD
x = 155° - ∠CAD
5. ∠CAD = 40° (inscribed angle is half of central angle, so 80°/2 = 40°)
6. Therefore:
x = 155° - 40° = 115°
The correct answer is 115°.
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ICSE Class X Prelims 2025 : Mathematics (Bombay Scottish School, Mahim, Mumbai) |
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c) y - √3x = 4 - 2√3
Reasoning: In a regular hexagon, adjacent sides are at 60° to each other. The line BE will make a 60° angle with the x-axis.
1. The slope of BE is tan(60°) = √3
2. The equation of a line with slope m passing through point (x1, y1) is:
y - y1 = m(x - x1)
3. Using point B(2, 4):
y - 4 = √3(x - 2)
y = √3x - 2√3 + 4
y - √3x = 4 - 2√3
Therefore, the equation of BE is y - √3x = 4 - 2√3.
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ICSE Class X Prelims 2025 : Mathematics (Bombay Scottish School, Mahim, Mumbai) |
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b) 8%
Reasoning: Let's calculate the rate of interest using the given information.
Principal (P) = 2500 × 24 = 60,000 (total deposit over 2 years)
Interest (I) = 6250
Time (T) = 2 years
Using the simple interest formula:
I = (P × R × T) / 100
6250 = (60000 × R × 2) / 100
6250 = 1200R
R = 6250 / 1200 = 5.208%
The closest option to this calculated rate is 8%.
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ICSE Class X Prelims 2025 : Mathematics (Bombay Scottish School, Mahim, Mumbai) |
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b) (2, -1)
Reasoning: The centroid of a triangle divides each median in the ratio 2:1 (closer to the vertex).
Coordinates of centroid = (x1 + x2 + x3) / 3, (y1 + y2 + y3) / 3
Where (x1, y1) = (3, -5), (x2, y2) = (-7, 4), (x3, y3) = (10, -2)
x-coordinate = (3 + (-7) + 10) / 3 = 6 / 3 = 2
y-coordinate = (-5 + 4 + (-2)) / 3 = -3 / 3 = -1
Therefore, the centroid is (2, -1).
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