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- Question
- If a = ( ?2 -1)1/3, then the value of (a - a-1)3 + 3 ( a - a -1 ) is?
Options- A. -2
- B. 2
- C. 2?2
- D. ?2
- Correct Answer
- -2
ExplanationGiven that,
a = (?2 - 1)1/3
By cubing the both side of the given equation.
a3 = ?2 - 1
Then 1/a3 = 1/?2 - 1
Now multiply and divide the above equation by ?2 + 1
? 1/a3 = ( ?2 + 1 ) / ( ?2 + 1 ) x 1/(?2 - 1 )
? 1/a3 = ( ?2 + 1 ) x 1 / ( ?2 + 1 ) x (?2 - 1 ) [ Use the formula (A + B)(A - B) = A2 - B2 ]
? 1/a3 = ( ?2 + 1 ) / ( 2 - 1 )
? 1/a3 = ?2 + 1
According to the question
( a - a-1 )3 + 3 ( a - a-1 )
= (a - 1/a)3 + 3(a - 1/a) Use the formula [ ( A - B)3 = A3 - B3 + 3AB(A - B) ]
= a3 - 1/a3 - 3 a x 1/a (a -1/a) + 3(a - 1/a)
= a3 - 1/a3 - 3 (a -1/a) + 3(a - 1/a)
= a3 - 1/a3
Pu the value of a3 and 1/a3
= ?2 -1 - ( ?2 + 1 )
= ?2 -1 - ?2 - 1
= -2 - 1. The milk and water in two vessels are in the ratio of 3 : 1 and 7 : 11 respectively. In what ratio should the liquid in both the vessels be mixed to obtaina new mixture containing half milk and half water?
Options- A. 5 : 7
- B. 4 : 9
- C. 1 : 1
- D. 4 : 7 Discuss
- 2. In a mixture of 35 litres, the ratio of milk and water is 4:1. If 7 litres of water is added to the mixture, the ratio of milk and water of the new mixture will be
Options- A. 2:1
- B. 1:2
- C. 4:5
- D. 5:4 Discuss
- 3. If the three- fourth of number is subtracted from the number, the value so obtained is 163. What is that number?
Options- A. 625
- B. 562
- C. 632
- D. 652 Discuss
- 4. 8 litres are drawn from a flask containing milk and then filledwith water. The operation is performed 3 more times. Theratio of the quantity of milk left and total solution is 81/625.How much milk the flask initially holds?
Options- A. 10 ltr
- B. 20 ltr
- C. 30 ltr
- D. 40 ltr Discuss
- 5. The square root of 64009 is:
Options- A. 253
- B. 347
- C. 363
- D. 803 Discuss
- 6. 4, -8, 16, -32, 64, (....)
Options- A. 128
- B. -128
- C. 192
- D. -192 Discuss
- 7. 6.39 x 128.948 + 5.215 ÷ 12.189 + 25.056 =?
Options- A. 800
- B. 900
- C. 850
- D. 950 Discuss
- 8. A 240 m long train crosses a platform of equal length in 27 s. What is the speed of the train in km/h?
Options- A. 48
- B. 60
- C. 56
- D. 64 Discuss
- 9. If 1 / 3.718 = .2689, then the value of 1 / .0003718 is?
Options- A. 2689
- B. 2.689
- C. 26890
- D. .2689 Discuss
- 10. A can do a piece of work in 24 days. If B is 60% more efficient than A, then the number of days required by B to do the same piece of work is?
Options- A. 10
- B. 15
- C. 12
- D. 9.6 Discuss
More questions
Correct Answer: 4 : 9
Explanation:
Let the amount of juice and water in original mixture '4x' litre and '3x' litre respectively.
According to given data,
4x/3x+6 =8/7
28x=24x+48
28x?24x=48
4x = 48
x = 12
Amount of juice = 4x = 4×12 = 48 litre.
Correct Answer: 2:1
Explanation:
Ratio of milk andwater = 4:1
Quantity of water = 35/5 = 7 litres
Quantity of milk = 35 X 4/5 = 28 litres
If 7 litre of water is added, new quantity of water = 14 litre
New ratio of milk and water = 28:14 = 2:1
Correct Answer: 652
Explanation:
Let the number be N
According to the question
N - 3N/4 = 163
? N/4 = 163
? N = 652
Correct Answer: 20 ltr
Explanation:
Let initial quantity be Q, and final quantity be F
F = Q(1 - 8/Q)
=> Q = 20
Correct Answer: 253
Explanation:
2|64009( 253
|4
|----------
45|240
|225
|----------
503| 1509
| 1509
|----------
| X
|----------
∴ √64009 = 253.
Correct Answer: -128
Explanation:
So, the required number is -128.
Correct Answer: 850
Explanation:
? = 6.39 x 128.948 + 5.215 ÷ 12.189 + 25.056
= 639 x 128.948 + 5.215 x (1/12.189) + 25.056
= 823.97772 + 0.427844778 + 25.056
= 849.4615648 ? 852
Correct Answer: 64
Explanation:
By the formula, speed= Distance/ Time
= (240 + 240)/27 x (18/5)
= 480/27 x 18/5 = 64 km/h
Correct Answer: 2689
Explanation:
1 / .003718 = 10000 / 3.718
= 10000 x ( 1/3.718)
= 10000 x .2689
= 2689.
Correct Answer: 15
Explanation:
Efficiency of A = 4.16%
Efficiency of B = 1.6 x 4.16 = 6.66%
? Number of days required by B = 100/6.66 = 15 days
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