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Find the sum of the first 10 terms of the following series, to the nearest integer.

15,30,60,dots
Answer:

Find the sum of the first 1010 terms of the following series, to the nearest integer.\newline15,30,60, 15,30,60, \ldots \newlineAnswer:

Full solution

Q. Find the sum of the first 1010 terms of the following series, to the nearest integer.\newline15,30,60, 15,30,60, \ldots \newlineAnswer:
  1. Identify type of series: Identify the type of series.\newlineThe given series is geometric because each term is multiplied by a common ratio to get the next term.
  2. Determine common ratio: Determine the common ratio rr of the series.\newlineTo find the common ratio, divide the second term by the first term.\newline3015=2\frac{30}{15} = 2\newlineCommon Ratio rr: 22
  3. Use formula for sum: Use the formula for the sum of the first nn terms of a geometric series.\newlineThe formula for the sum of the first nn terms (SnS_n) of a geometric series is:\newlineSn=a(1rn)/(1r)S_n = a \cdot (1 - r^n) / (1 - r), where aa is the first term and rr is the common ratio.
  4. Plug values into formula: Plug the values into the formula to find the sum of the first 1010 terms.a=15a = 15 (the first term)r=2r = 2 (the common ratio)n=10n = 10 (the number of terms)S10=15×(1210)/(12)S_{10} = 15 \times (1 - 2^{10}) / (1 - 2)
  5. Calculate sum: Calculate the sum using the values from Step 44.\newlineS10=15×(11024)/(12)S_{10} = 15 \times (1 - 1024) / (1 - 2)\newlineS10=15×(1023)/(1)S_{10} = 15 \times (-1023) / (-1)\newlineS10=15×1023S_{10} = 15 \times 1023\newlineS10=15345S_{10} = 15345
  6. Round sum: Round the sum to the nearest integer. The sum is already an integer, so no rounding is necessary.

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