Major Competitive Exams
Q. If the circumradius of triangle ABC is 10 cm and the area is 48 cm², what is the length of the side opposite to angle A?
A.
12 cm
B.
14 cm
C.
16 cm
D.
18 cm
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Solution
Using the formula R = (abc)/(4 * Area), we can find the side opposite to angle A. Let a = side opposite to A. Then, a = (4 * Area * R) / (bc) = (4 * 48 * 10) / (b * c).
Correct Answer: B — 14 cm
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Q. If the circumradius R of triangle ABC is 5 cm, what is the maximum area of the triangle?
A.
12.5 cm²
B.
15 cm²
C.
20 cm²
D.
25 cm²
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Solution
The maximum area of a triangle with circumradius R is given by the formula Area = (abc)/(4R). For maximum area, the triangle should be equilateral, thus Area = (3√3/4) * (R^2) = (3√3/4) * (5^2) = 25√3/4 cm².
Correct Answer: C — 20 cm²
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Q. If the coefficient of x^k in the expansion of (x + 1)^n is given by C(n,k), what does C(n,k) represent?
A.
The number of ways to choose k items from n.
B.
The total number of terms in the expansion.
C.
The sum of the coefficients.
D.
The product of the coefficients.
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Solution
C(n,k) represents the number of ways to choose k items from n, which corresponds to the coefficient of x^k.
Correct Answer: A — The number of ways to choose k items from n.
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Q. If the concentration of a reactant is tripled in a second-order reaction, how does the rate change? (2023)
A.
Increases by 3 times
B.
Increases by 6 times
C.
Increases by 9 times
D.
Increases by 12 times
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Solution
For a second-order reaction, if concentration is tripled, the rate increases by 3² = 9 times.
Correct Answer: C — Increases by 9 times
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Q. If the concentration of Cu²⁺ in a cell is increased, what happens to the cell potential?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
Increasing the concentration of Cu²⁺ increases the cell potential according to the Nernst equation.
Correct Answer: A — Increases
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Q. If the concentration of reactants is increased in a system at equilibrium, what will happen to the position of equilibrium?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Depends on temperature
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Solution
According to Le Chatelier's principle, increasing the concentration of reactants will shift the equilibrium position to the right, favoring the formation of products.
Correct Answer: A — Shift to the right
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Q. If the coordinates of a point are (x, y) and it lies on the line 2x + 3y = 12, what is the value of y when x = 2?
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Solution
Substituting x = 2: 2(2) + 3y = 12 => 4 + 3y = 12 => 3y = 8 => y = 8/3 ≈ 2.67, closest is 3.
Correct Answer: B — 3
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Q. If the coordinates of a point are (x, y) and it lies on the line 3x + 4y = 12, what is y when x = 0?
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Solution
Substituting x = 0: 3(0) + 4y = 12 => 4y = 12 => y = 3.
Correct Answer: B — 4
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Q. If the coordinates of point A are (1, 2) and point B are (4, 6), what is the length of AB? (2023)
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Solution
Length AB = √[(4-1)² + (6-2)²] = √[9 + 16] = √25 = 5.
Correct Answer: A — 5
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Q. If the coordinates of point C are (5, 5) and point D are (5, 10), what is the length of CD? (2021)
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Solution
Length CD = |10 - 5| = 5.
Correct Answer: A — 5
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Q. If the coordinates of point C are (5, 5) and the slope of the line is 1, what is the equation of the line? (2021) 2021
A.
y = x
B.
y = 5
C.
y = 2x - 5
D.
y = x + 5
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Solution
Using point-slope form: y - 5 = 1(x - 5) => y = x.
Correct Answer: A — y = x
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Q. If the coordinates of points A and B are (1, 2) and (3, 4) respectively, what is the distance AB?
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Solution
Distance AB = √((3-1)² + (4-2)²) = √(4) = 2.
Correct Answer: A — 2√2
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Q. If the coordinates of points A and B are (1, 2) and (4, 6) respectively, what is the distance AB?
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Solution
Distance AB = √((4-1)² + (6-2)²) = √(9 + 16) = √25 = 5.
Correct Answer: A — 5
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Q. If the coordinates of the vertices of a triangle are (1, 1), (4, 5), and (7, 2), what is the perimeter of the triangle?
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Solution
Calculate distances AB, BC, CA and sum them: AB = 5, BC = 5, CA = 7. Perimeter = 5 + 5 + 7 = 17.
Correct Answer: B — 14
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Q. If the coordinates of the vertices of a triangle are (1, 2), (3, 4), and (5, 2), what is the perimeter of the triangle?
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Solution
Perimeter = AB + BC + CA = √[(3-1)² + (4-2)²] + √[(5-3)² + (2-4)²] + √[(1-5)² + (2-2)²] = 2.83 + 2.83 + 4 = 10.
Correct Answer: B — 10
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Q. If the coordinates of the vertices of a triangle are (1, 2), (4, 6), and (7, 2), what is the perimeter of the triangle?
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Solution
Perimeter = AB + BC + CA = √[(4-1)² + (6-2)²] + √[(7-4)² + (2-6)²] + √[(1-7)² + (2-2)²] = 3 + √(9 + 16) + 6 = 3 + 5 + 6 = 14.
Correct Answer: B — 14
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Q. If the coordinates of the vertices of a triangle are A(1, 1), B(4, 5), and C(7, 2), what is the area of the triangle?
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Solution
Area = 1/2 | x1(y2-y3) + x2(y3-y1) + x3(y1-y2) | = 1/2 | 1(5-2) + 4(2-1) + 7(1-5) | = 1/2 | 3 + 4 - 28 | = 1/2 * 21 = 10.5.
Correct Answer: B — 12
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Q. If the cost function is C(x) = 3x^2 + 12x + 5, find the minimum cost. (2020)
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Solution
The minimum cost occurs at x = -b/(2a) = -12/(2*3) = -2. C(-2) = 3(-2)^2 + 12(-2) + 5 = 8.
Correct Answer: B — 8
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Q. If the cost function is C(x) = 3x^2 + 12x + 5, find the minimum cost. (2020) 2020
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Solution
The minimum cost occurs at x = -b/(2a) = -12/(2*3) = -2. C(-2) = 3(-2)^2 + 12(-2) + 5 = 8.
Correct Answer: B — 8
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Q. If the cost function is C(x) = 5x^2 + 20x + 100, find the minimum cost. (2020)
A.
100
B.
120
C.
140
D.
160
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Solution
The minimum cost occurs at x = -b/(2a) = -20/(2*5) = -2. C(-2) = 5(-2)^2 + 20(-2) + 100 = 120.
Correct Answer: B — 120
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Q. If the critical angle for a certain material is 30°, what is the refractive index of that material?
A.
1.00
B.
1.15
C.
1.73
D.
2.00
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Solution
The refractive index n can be calculated using n = 1/sin(θc). For θc = 30°, n = 1/sin(30°) = 1/0.5 = 2.00.
Correct Answer: C — 1.73
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Q. If the critical angle for a certain material is 45°, what is the refractive index of that material?
A.
1.41
B.
1.00
C.
1.73
D.
0.71
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Solution
Using the formula n = 1/sin(θc), where θc = 45°, we find n = 1/sin(45°) = 1/0.7071 ≈ 1.41.
Correct Answer: A — 1.41
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Q. If the cross-sectional area of a wire is doubled, how does its resistance change?
A.
Doubles
B.
Halves
C.
Remains the same
D.
Increases four times
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Solution
Resistance is inversely proportional to cross-sectional area; doubling the area halves the resistance.
Correct Answer: B — Halves
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Q. If the cross-sectional area of a wire is doubled, what happens to its resistance?
A.
Doubles
B.
Halves
C.
Remains the same
D.
Increases four times
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Solution
Resistance (R) is inversely proportional to cross-sectional area (A). Doubling A halves the resistance.
Correct Answer: B — Halves
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Q. If the current flowing through a resistor is 2A and the voltage across it is 6V, what is the resistance? (2022)
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Solution
Using Ohm's Law, R = V / I = 6V / 2A = 3Ω.
Correct Answer: A — 3Ω
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Q. If the current in a circuit is 5 A and the resistance is 2 ohms, what is the power consumed in the circuit?
A.
10 W
B.
25 W
C.
5 W
D.
2.5 W
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Solution
Power (P) can be calculated using P = I^2R = (5 A)^2 * 2 Ω = 25 W.
Correct Answer: B — 25 W
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Q. If the current in a circuit is doubled while the resistance remains constant, what happens to the voltage?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Ohm's Law, if the current (I) is doubled and resistance (R) remains constant, the voltage (V) must also double.
Correct Answer: A — It doubles
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Q. If the current in a circuit is halved, what happens to the power consumed by the circuit?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
Power P = I^2 * R. If I is halved, P becomes (1/2)^2 * R = 1/4 * P, so the power is reduced to a quarter, which means it halves.
Correct Answer: B — It halves
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Q. If the current in a circuit is split into two branches with resistances R1 = 2Ω and R2 = 4Ω, what is the current through R1 if the total current is 6A?
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Solution
Using the current division rule, I1 = I_total * (R2 / (R1 + R2)) = 6A * (4Ω / (2Ω + 4Ω)) = 6A * (4/6) = 4A.
Correct Answer: B — 3A
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Q. If the current in a circular loop is doubled, how does the magnetic field at the center of the loop change?
A.
It remains the same
B.
It doubles
C.
It quadruples
D.
It halves
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Solution
The magnetic field at the center of a circular loop is directly proportional to the current; thus, if the current is doubled, the magnetic field also doubles.
Correct Answer: B — It doubles
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