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If the sum of the first four terms of an...

If the sum of the first four terms of an AP is 40 and the sum of the first fourteen terms of an AP is 280. Find the sum of first n terms of the A.P.

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The correct Answer is:
`n(n + 6) " or " n^(2) + 6n`
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EDUCART PUBLICATION-ARITHMETIC PROGRESSIONS-LONG ANSWER TYPE QUESTIONS
  1. How many terms of the arithmetic progression 45, 39, 33,….. Must be ta...

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  2. Show that the sum of an AP whose first term is a, the second term b an...

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  3. If the sum of the first four terms of an AP is 40 and the sum of the f...

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  4. The sum of the 4th and 8th terms of an AP is 24 and the sum of the ...

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  5. If the ratio of the 11^(th) term of an AP to its 18^(th) term is 2 : 3...

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  6. The ratio of the sums of m terms and n terms of an A.P. is m^(2) : n^(...

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  7. Solve the equation -4+(-1)+2+ … +x =437.

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  8. A thief runs with a uniform speed of 100 m/min. After one minute a pol...

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  9. If the ratio of the sum of the first n terms of two Aps is (7n + 1) : ...

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  10. The 26th, 11th and the last terms of an AP are, 0, 3 and -(1)/(5),resp...

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  11. Find the sum of the following series : 5+(-41)+9+(-39)+13+(-37)+17+....

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  12. The sum of four consecutive numbers in A.P. is 32 and the ratio of the...

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  13. Solve for x: 1+4+7+10+...+x=287

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  14. The sum of the first five terms of an A.P. and the sum of the first s...

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  15. Find the (i) sum of those integers between 1 and 500 which are multi...

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  16. Find the (i) sum of those integers between 1 and 500 which are multi...

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  17. Find the (i) sum of those integers between 1 and 500 which are multi...

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  18. An AP consists of 37 terms. The sum of the three middle most terms is ...

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  19. If the sum of first p terms of an A.P. is equal to the sum of the firs...

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  20. Find the sum of the integers between 100 and 200 that are divisible by...

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