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- Question
A can do a piece of work in 4 hours; B and C together can do it in 3 hours, while A and C together can do it in 2 hours. How long will B alone take to do it?
Options- A. 8 hours
- B. 10 hours
- C. 12 hours
- D. 24 hours
- Correct Answer
- 12 hours
ExplanationA's 1 hour's work = 1 ; 4 (B + C)'s 1 hour's work = 1 ; 3 (A + C)'s 1 hour's work = 1 . 2 (A + B + C)'s 1 hour's work = ❨ 1 + 1 ❩ = 7 . 4 3 12 B's 1 hour's work = ❨ 7 - 1 ❩ = 1 . 12 2 12 ∴ B alone will take 12 hours to do the work.
More questions
- 1. Five coins are tossed at a time. Then, the probability of obtaining at least one tail is
Options- A. 31/32
- B. 1/32
- C. 1/5
- D. 5/32 Discuss
Correct Answer: 31/32
Explanation:
Total events = n (s) = 25 = 32
n(E) of getting heads = 1
p(E) = 1/32
? n(E) = 1 - p(E) = 1 - 1/32 = 31/32- 2. Find the maximum number of tree which can plant 20 m apart on the two side of straight road 1760 m long
Options- A. 174
- B. 176
- C. 180
- D. 178 Discuss
Correct Answer: 178
Explanation:
Number of trees that can be planted on one side of road = (1760 / 20) + 1
= 88 + 1
=89
? Trees on the both side = 2 x 89=178- 3. 1307 x 1307 =?
Options- A. 1601249
- B. 1607249
- C. 1701249
- D. 1708249 Discuss
Correct Answer: 1708249
Explanation:
1307 x 1307 = (1307)2
= (1300 + 7 )2
= (1300)2 + (7)2 + 2 x 1300 x 7
= 1690000 + 49 +18200
= 1708249- 4. The circumferences of two concentric are 176 m and 132 m respectively. what is the difference between their radii?
Options- A. 5 meter
- B. 7 meter
- C. 8 meter
- D. 44 meter Discuss
Correct Answer: 7 meter
Explanation:
? 2?R - 2?r = (176-132)
? 2?(R-r) = 44
? R-r = ( 44 x 7 )/ (2 x 22)
= 7 m- 5. (1/2 ÷ 4 + 20) / (1/2 x 4 + 20) =?
Options- A. 81 / 88
- B. 23/11
- C. 161 / 176
- D. 1 Discuss
Correct Answer: 161 / 176
Explanation:
Given Exp. = (1/2 x 1/4 + 20) / (2 + 20) = (161/8) x (1/22)
= 161 / 176- 6. Find the cardinal number of the following set {x: x = 2n, n ? N, 4 ? x ? 11}
Options- A. 8
- B. 6
- C. 12
- D. 4 Discuss
Correct Answer: 4
Explanation:
NA
- 7. If a fraction is multiplied by itself and then divided by the reciprocal of the same fraction, the result is 18 26/ 27. Find the fraction.
Options- A. 8/27
- B. 11/3
- C. 22/3
- D. 32/3 Discuss
Correct Answer: 22/3
Explanation:
If the required fraction be P
According to the question
(P x P) / (1/P) = 1826/27
? P3 = 512/27
? P = 8/3 = 22/3- 8. (0.04) 3 =?
Options- A. 0.064
- B. 0.0064
- C. 0.00064
- D. 0.000064 Discuss
Correct Answer: 0.000064
Explanation:
(0.04)3 = 0.04 x 0.04 x 0.04
= 0.000064- 9. If a + b + c = 8, then the value of (a ? 4)3 + (b ? 3)3 + (c ? 1)3 ? 3 (a ? 4) (b ? 3) (c ? 1) is
Options- A. 2
- B. 4
- C. 1
- D. 0 Discuss
Correct Answer: 0
Explanation:
We have p3 + q3 + r3 ? 3pqr = (p + q + r) (p2 + q2 + r2 ?pq ? qr - rp)
Here p = a ? 4, q = b ? 3, r = c ?1
So, given expression is (p + q + r) (p2 + q2 + r2 ? pq ? qr ? rp)
= (a ? 4 + b ? 3 + c ? 1) (p2 + q2 + r2 ? pq ? qr ? rp)
= (a + b + c ? 8) (p2 + q2 + r2 ? pq ? qr ? rp)
= (8 ? 8) (p2 + q2 + r2 ? pq ? qr ? rp)
? (a ? 4)3 + (b ? 3)3 + (c ? 1)3 ? 3 (a ? 4) (b ? 3) (c ? 1) = 0- 10. 3571 +? - 6086 = 155
Options- A. 2400
- B. 2630
- C. 2515
- D. None of these Discuss
Correct Answer: 2630
Explanation:
Let 3571 + x - 6086 = 115
Then, x = 6086 +115 -3571
= 6201-3571
= 2630
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