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Find the sum of the first 45 terms of the following series, to the nearest integer.

2,7,12,dots
Answer:

Find the sum of the first 4545 terms of the following series, to the nearest integer.\newline2,7,12, 2,7,12, \ldots \newlineAnswer:

Full solution

Q. Find the sum of the first 4545 terms of the following series, to the nearest integer.\newline2,7,12, 2,7,12, \ldots \newlineAnswer:
  1. Identify pattern: Identify the pattern in the series.\newlineThe series starts at 22 and each term increases by 55. This is an arithmetic series with a common difference (dd) of 55.
  2. Find terms: Find the first term a1a_1 and the common difference dd of the series.\newlineThe first term a1a_1 is 22 and the common difference dd is 55.
  3. Use formula: Use the formula for the sum of the first nn terms of an arithmetic series: Sn=n2×(2a1+(n1)d)S_n = \frac{n}{2} \times (2a_1 + (n - 1)d). We need to find the sum of the first 4545 terms, so n=45n = 45.
  4. Substitute values: Substitute the values into the formula. S45=452×(2×2+(451)×5)S_{45} = \frac{45}{2} \times (2\times2 + (45 - 1)\times5)
  5. Perform calculations: Perform the calculations inside the parentheses first. S45=452×(4+44×5)S_{45} = \frac{45}{2} \times (4 + 44\times5)
  6. Multiply 4444: Multiply 4444 by 55. \newlineS45=452×(4+220)S_{45} = \frac{45}{2} \times (4 + 220)
  7. Add 44: Add 44 to 220220. \newlineS45=452×224S_{45} = \frac{45}{2} \times 224
  8. Multiply 224224: Multiply 224224 by 4545 and then divide by 22. \newlineS45=224×452S_{45} = \frac{224 \times 45}{2}
  9. Perform multiplication: Perform the multiplication. S45=100802S_{45} = \frac{10080}{2}
  10. Divide by 22: Divide 1008010080 by 22 to get the final sum.\newlineS45=5040S_{45} = 5040

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