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- Question
- If one of the roots of the equation x 2 - bx + c = 0 is the square of the other, then which of the following option is correct?
Options- A. b3 = 3bc + c2 + c
- B. c3 = 3bc + b2 + b
- C. 3bc = c3 + b2 + b
- D. 3bc = c3 + b3 + b2
- Correct Answer
- b3 = 3bc + c2 + c
ExplanationGiven that, one root of the equation
x2 - bx + c = 0 is square of other root of this equation i.e., roots (?, ?2).
? Sum of roots = ? + ?2 = -(-b)/1
? ? (? + 1) = b .......(i)
and product of roots= ?. ?2 = c/1
? ?3 = c ? = c1/3 ....(ii)
From Eqs. (i) and (ii).
c1/3 (c1/3 + 1) = b ....(iii)
On cubing both sides, we get
c(c1/3 + 1)3 = b3
? c {c + 1 + 3c1/3 (c1/3 + 1)} = b3
? c {c + 1 = 3b} = b3 [from Eq. (iii)]
? b3 = 3bc + c2 + c - 1. A train 300 meters long passes a standing man is 15 seconds. The speed of the train is?
Options- A. 40 km/hr
- B. 50 km/hr
- C. 60 km/hr
- D. 72 km/hr Discuss
- 2. If the diagonal of a square is double, how does the area of the square change?
Options- A. Becomes four fold
- B. Becomes three fold
- C. Becomes two fold
- D. None of the above Discuss
- 3. 46080, 3840, 384, 48, 24, 2, 1
Options- A. 1
- B. 2
- C. 24
- D. 384 Discuss
- 4. The difference between the length and breadth of a rectangle is 23 m. If its perimeter is 206 m, then its area is:
Options- A. 1520 m2
- B. 2420 m2
- C. 2480 m2
- D. 2520 m2 Discuss
- 5. 4/5 of a number exceeds its 2/3 by 8. The number is?
Options- A. 30
- B. 60
- C. 90
- D. None of these Discuss
- 6. Find the angle between minute hand and hour hand at 2 : 18 AM
Options- A. 37°
- B. 33°
- C. 39°
- D. None of these Discuss
- 7. Rakesh, Dinesh and Mahesh start a business by investing ? 5000 , ? 8000 and ? 12000 , respectively . At the end of year, they got the profit of ? 12500. What is the share of Dinesh in profit?
Options- A. ? 4000
- B. ? 4500
- C. ? 6000
- D. ? 7500 Discuss
- 8. The least multiple of 7, which leaves a remainder of 4, when divided by 6, 9, 15 and 18 is:
Options- A. 74
- B. 94
- C. 184
- D. 364 Discuss
- 9. If log 27 = 1.431, then the value of log 9 is:
Options- A. 0.934
- B. 0.945
- C. 0.954
- D. 0.958 Discuss
- 10. A box contains 2 white balls, 3 black balls and 4 red balls. In how many ways can 3 balls be drawn from the box, if at least one black ball is to be included in the draw?
Options- A. 32
- B. 48
- C. 64
- D. 96
- E. None of these Discuss
More questions
Correct Answer: 72 km/hr
Explanation:
? Speed = Distance / Time = (300/15)
= 20 m/sec
= (20 x 18) / 5 = 72 km/hr
Correct Answer: Becomes four fold
Explanation:
Ratio of the areas = area of original square / area of new square
= [ d2 / 2 ] / [ (2d)2 / 2 ] = 1/4
? New area becomes 4 fold.
Correct Answer: 24
Explanation:
So, 24 is wrong, it should be 8 (48/6 = 8).
Correct Answer: 2520 m2
Explanation:
Solving the two equations, we get: l = 63 and b = 40.
∴ Area = (l x b) = (63 x 40) m2 = 2520 m2.
Correct Answer: 60
Explanation:
Let the number be x,
Then, 4x/5 - 2x/3 = 8
? (12x - 10x) / 15 = 8
? 2x = 120
? x = 60
Correct Answer: 39°
Explanation:
39°
Correct Answer: ? 4000
Explanation:
Share of Rakesh : Share of Dinesh : Share of Mahesh
= 5000 : 8000 : 12000 = 5 : 8 : 12
Total earned profit = ? 12500
? Share of Dinesh in profit
= [8/(5 + 8 + 12)] x 12500 = (8/25) x 12500
= 8 x 500 = ? 4000
Correct Answer: 364
Explanation:
L.C.M. of 6, 9, 15 and 18 is 90.
Let required number be 90k + 4, which is multiple of 7.
Least value of k for which (90k + 4) is divisible by 7 is k = 4.
∴ Required number = (90 x 4) + 4 = 364.
Correct Answer: 0.954
Explanation:
⟹ log (33 ) = 1.431
⟹ 3 log 3 = 1.431
⟹ log 3 = 0.477
∴ log 9 = log(32 ) = 2 log 3 = (2 x 0.477) = 0.954.
Correct Answer: 64
Explanation:
| ∴ Required number of ways | = (3C1 x 6C2) + (3C2 x 6C1) + (3C3) | |||||||||||||
|
||||||||||||||
| = (45 + 18 + 1) | ||||||||||||||
| = 64. |
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