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- Question
- The mean weight of 150 students in class is 60 kg. The mean weight of boys is 70 kg and that of girls is 55 kg. What is the number of boys in the class?
Options- A. 50
- B. 60
- C. 75
- D. 100
- Correct Answer
- 50
ExplanationGiven that total number of students = 150 = ( n1+ n2) and
Mean weight of 150 students = 60 kg.
The mean weight of boys a1= 70 kg and
The mean weight of girls a2 = 55 kg
Let n1 and n2 be the number of boys and girl, respectively.
? n1 + n2 = 150 ...(i)
11 n1 + 11 n2 = 1650 ...(ii)
Average weight = (n1 a1 + n2 a2) / (n1 + n2)
? 60 = (70 n1 + 55n2)/150
? 70 n1 + 55n2 = 9000
? 14n1 + 11n2 =1800 ...(iii)
On subtracting Eq. (ii) from Eq. (iii), we get
3n1 = 150 ? n1 = 50
Hence, required number of boys is 50. - 1. 0.0169 / 0.013=?
Options- A. .13
- B. .013
- C. 1.3
- D. 13 Discuss
- 2. Two posts are x meter apart and the height of one is double that of the other. If from the midpoint of the line joining their feet, an observer finds the angular elevations of their tops to be complementary, then the height (in meter) of the shorter post is :
Options- A. x 2 ?2
- B. x 4
- C. x ?2
- D. x ?2 Discuss
- 3. If p/q =4/5, then the value of 4/7 + {(2q - p) / (2q + p)} is?
Options- A. 3 / 7
- B. 34
- C. 1
- D. 2 Discuss
- 4. What is 25% of 25% is equal to?
Options- A. 6.25
- B. .625
- C. .0625
- D. .000625 Discuss
- 5. The number .05 is hoe many percent of 20?
Options- A. 25
- B. .025
- C. .25
- D. 2.5 Discuss
- 6. Find the lowest common multiple of 24, 36 and 40.
Options- A. 120
- B. 240
- C. 360
- D. 480 Discuss
- 7. 8 1/ 3% expressed as a fraction is?
Options- A. 25/3
- B. 3/25
- C. 1/12
- D. 1/4 Discuss
- 8. .025 in terms of term of rate per cent is?
Options- A. .25%
- B. 2.5%
- C. 0.25%
- D. 371/2% Discuss
- 9. What percentage of 2/7 is 1/35?
Options- A. 2.5%
- B. 10%
- C. 25%
- D. 20% Discuss
- 10. A sum of ? 4000 is lent out in two parts, one at 8% simple interest and other at 10% simple interest. If the annual interest is ? 352, the sum lent at 8% is
Options- A. ? 1600
- B. ? 2400
- C. ? 1800
- D. ? 2800 Discuss
More questions
Correct Answer: 1.3
Explanation:
0.0169 / 0.0130 = 169 / 130
= 13 / 10
Correct Answer: x 2 ?2
Explanation:
Correct Answer: 1
Explanation:
Given Exp. = 4 / 7 + {(2q - p) / (2q + p)}
Dividing numerator as well as denominator by q,
Exp = 4/7 + {2-p/q) / (2 + p/q)}
= 4/7 + {(2 - 4/5) / (2 + 4/5)}
= 4/7 + 6/14
= 4/7 + 3/7
=7/7
=1.
Correct Answer: .0625
Explanation:
25% of 25% = (25/100) x (25/100) = 625/10000 = 0.625
Correct Answer: .25
Explanation:
Let y% of 20 = .05
Then, (y x 20)/100 = .05
? y = .25
Correct Answer: 360
Explanation:
2 | 24 - 36 - 40 -------------------- 2 | 12 - 18 - 20 -------------------- 2 | 6 - 9 - 10 ------------------- 3 | 3 - 9 - 5 ------------------- | 1 - 3 - 5 L.C.M. = 2 x 2 x 2 x 3 x 3 x 5 = 360.
Correct Answer: 1/12
Explanation:
81/3% = (25/3 x 1/100) = 1/12
Correct Answer: 2.5%
Explanation:
.025 = (25/1000) x 100% = 2.5%
Correct Answer: 10%
Explanation:
Let N% of 2/7 is 1/35
? (2/7 x N) / 100 = 1/35
? N = 1/35 x 7/2 x 100 = 10%
Correct Answer: ? 2400
Explanation:
Let the money interest at 8% interest be ? P .
Then, the money interest at 10% interest = ?(4000 - P)
According to the question,
(P x 8 x 1)/100 + [(4000 - P) x 10 x 1]/100 = 352
? 8P + 40000 - 10P = 35200
? 40000 - 35200 = 2P
? P = 4800/2 = ? 2400
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