1.
The sum of n terms of an A.P. is 3n2 + n, find the nth term.
- A.6n - 4
- C.4n - 4
- B.6n - 2
- D.4n - 2
- Answer & Explanation
- Report
Answer : [B]
Explanation :
Explanation :
| Given Sn = 3n2 + n, put n = 1, 2 |
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| S1 = 3.12 + 1 = 4 | |||||
| T1 = 4 | |||||
| S2 = 3.22 + 2 = 14 | |||||
| T2 = S2 - S1 = 14 - 4 = 10 | |||||
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2.
Find the sun of the following series
3 + 7 + 11 + 15 + . To 30 terms
3 + 7 + 11 + 15 + . To 30 terms
- A.1920
- C.1970
- B.1830
- D.1740
- Answer & Explanation
- Report
Answer : [B]
Explanation :
Explanation :
| The given series is 3 + 7 + 11 + 15 + to 30 terms. | ||||||
| a = 3, d = 4, n = 30 | ||||||
| We know that | ||||||
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| = 15 [6 + 116] | ||||||
| = 1830 | ||||||
3.
Find the position of 62 in the following series 2, 5, 8, ....?
- A.26
- C.21
- B.23
- D.20
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| It is an A.P. series with a = 2, d = 3 | |||||||
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| But we know that Tn = a + (n 1) d | |||||||
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| or 62 = 2 + 3n 3 |
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| or 62 2 + 3 = 3n | |||||||
| or 63 = 3n |
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| or 3n = 63 |
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| or n = 21 |
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| 62 is the 21st term | |||||||
4.
If you save 1 paise totay, 2 paise next day and 3 paise the succeeding day and so on, what will be your savings in 365 days?
- A.666.75
- C.665.35
- B.668.85
- D.667.95
- Answer & Explanation
- Report
Answer : [D]
Explanation :
Explanation :
| Savings on successive days are 1, 2, 3, 4 . Paise which form and A.P. with a = 1, d =1 | ||||||
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| = 66795 paise | ||||||
| = Rs. 667.95 | ||||||
5.
Find the sun of the following series
72 + 70 + 68 + . + 40
72 + 70 + 68 + . + 40
- A.886
- C.952
- B.918
- D.988
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| The given series is 72 + 70 + 68 + .... + 40 | ||||||||||
| a = 72, d = -2, l = 40 | ||||||||||
| We know: l = a + (n 1) d, putting values of a, d and l |
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| 40 = 72 + (n 1) (-2) = 74 2n |
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| or 2n = 34 |
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