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- Question
The sum of first 45 natural numbers is:
Options- A. 1035
- B. 1280
- C. 2070
- D. 2140
- Correct Answer
- 1035
Explanation
Let S n =(1 + 2 + 3 + ... + 45). This is an A.P. in which a =1, d =1, n = 45.Sn = n [2a + (n - 1)d] = 45 x [2 x 1 + (45 - 1) x 1] = ❨ 45 x 46 ❩ = (45 x 23) 2 2 2 = 45 x (20 + 3)
= 45 x 20 + 45 x 3
= 900 + 135
= 1035.
Shorcut Method:
Sn = n(n + 1) = 45(45 + 1) = 1035. 2 2 - 1. Aarti can do a piece of work in 6 days. In how many days will she complete three time of work of same type?
Options- A. 18 days
- B. 21 days
- C. 3 days
- D. 6 days Discuss
- 2. 750.0003 ÷ 19.999 =?
Options- A. 49
- B. 18
- C. 22
- D. 38 Discuss
- 3. 105, 85, 60, 30, 0, - 45, - 90?
Options- A. 0
- B. 85
- C. -45
- D. 60 Discuss
- 4. Let A = {1, 2, {3, 4}, 5}. Which of the following statements is true?
Options- A. {3, 4} ? A
- B. {3, 4} ? A
- C. 1 ? A
- D. {1, 2, 5} ? A Discuss
- 5. Two vessels A and B contains milk and water mixed in the ratio 5 : 3 and 2 : 3. When these mixtures are mixed to form a new mixture containing half milk and half water, they must be taken in the ratio ?
Options- A. 2 : 5
- B. 3 : 5
- C. 4 : 5
- D. 7 : 3 Discuss
- 6. 1, 2, 4, 8, 16, 32, 64, (...), 256?
Options- A. 148
- B. 128
- C. 154
- D. 164 Discuss
- 7. A tree is 12 m tall and casts an an 8 m long shadow. At the same time, a flag pole caste a 100 m long shadow. How long is the flag pole?
Options- A. 150 m
- B. 200 m
- C. 125 m
- D. 115 m Discuss
- 8. 8% of 96 =? of 1/25
Options- A. 19.2
- B. 7.68
- C. 1.92
- D. None of these Discuss
- 9. A certain amount earns simple interest of Rs. 1750 after 7 years. Had the interest been 2% more, how much more interest would it have earned?
Options- A. Rs. 35
- B. Rs. 245
- C. Rs. 350
- D. Cannot be determined
- E. None of these Discuss
- 10. If the hands of a clock coincide in every 65 minutes (true time), in 24 hours the clock will gain:
Options- A. 10 10 minutes. 143
- B. 9 12 minutes. 143
- C. 11 12 minutes. 143
- D. 12 10 minutes. 143 Discuss
More questions
Correct Answer: 18 days
Explanation:
We have the important relation, More work, More time (days)
? A piece of work can be done in 6 days.
? Three times of work of same type can be done in 6 x 3
= 18 days
Correct Answer: 38
Explanation:
? = 750.0003 ÷ 19.999
? ? ? 750 ÷ 20
? ? ? 375 ? 38
Correct Answer: 0
Explanation:
Subtract 20, 25, 30, 35, 40, 45 from successive numbers. So 0 is wrong.
Correct Answer: {3, 4} ? A
Explanation:
NA
Correct Answer: 4 : 5
Explanation:
Correct Answer: 128
Explanation:
Each previous number is multiplied by 2.
Correct Answer: 150 m
Explanation:
? 8 m shadow means original height = 12 m
? 1 m shadow means original height = 12/8 m
? 100 m shadow means original height = (12/8) x 100 m
= (6/4) x 100 = 6 x 25 = 150 m
Correct Answer: None of these
Explanation:
Let 8% of 96 = y of 1/25
? (8 x 96)/100 = y/25
? y = (8 x 96 x 25)/100 = 192
Correct Answer: Cannot be determined
Explanation:
We need to know the S.I., principal and time to find the rate.
Since the principal is not given, so data is inadequate.
Correct Answer: 10 10 minutes. 143
Explanation:
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