Maths MCQs for AD (ASF) – Series 12 (Q151-160)
Q151. If x + 1/x = 5, find the value of x² + 1/x².
- A) 23
- B) 25
- C) 21
- D) None of these
Answer: A
x²+1/x² = (x+1/x)² − 2 = 25−2 = 23.
Q152. Solve for x: 2x² − 7x + 3 = 0. Find the sum of the roots.
- A) 4
- B) 3.5
- C) 3
- D) None of these
Answer: B
Sum of roots = −b/a = 7/2 = 3.5.
Q153. Find the next number in the series: 2, 6, 12, 20, 30, ?
- A) 44
- B) 42
- C) 40
- D) None of these
Answer: B
Differences are 4, 6, 8, 10, 12; next term = 30+12 = 42.
Q154. Find the missing number in the series: 3, 9, 27, 81, ?
- A) 252
- B) 234
- C) 243
- D) None of these
Answer: C
Each term is multiplied by 3; next term = 81×3 = 243.
Q155. If a:b = 2:3 and b:c = 4:5, find a:b:c.
- A) 8:12:15
- B) 2:3:5
- C) 6:9:15
- D) None of these
Answer: A
Scale a:b to 8:12 and b:c to 12:15 (matching b); so a:b:c = 8:12:15.
Q156. The sum of three consecutive even numbers is 90. Find the largest number.
- A) 32
- B) 34
- C) 30
- D) None of these
Answer: A
Let numbers be n−2, n, n+2; 3n = 90 → n = 30; largest = 32.
Q157. Find the value of (25)^(1/2) × (16)^(1/2).
- A) 20
- B) 18
- C) 22
- D) None of these
Answer: A
√25 × √16 = 5×4 = 20.
Q158. If 3x − 5 = 2x + 7, find the value of x.
- A) 10
- B) 12
- C) 14
- D) None of these
Answer: B
3x−2x = 7+5 → x = 12.
Q159. Look at this series: 7, 10, 8, 11, 9, 12, ? What number should come next?
- A) 9
- B) 10
- C) 13
- D) None of these
Answer: B
The pattern alternates +3, −2; after 12 the next step is −2, giving 10.
Q160. A number consists of two digits whose sum is 9. If 27 is subtracted from the number, the digits are reversed. Find the number.
- A) 72
- B) 54
- C) 63
- D) None of these
Answer: C
Let the number be 10a+b with a+b=9. 10a+b−27=10b+a gives a−b=3; solving, a=6, b=3; number = 63.
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