Suav just started a running plan where he runs 20 miles the first week and then increases the number of miles he runs by \( 5 \% \) each week. If he keeps up this plan for 25 weeks, how many total miles would Suav have run, to the nearest whole number?
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To find the total miles Suav runs over 25 weeks, we can represent the number of miles he runs each week as a geometric series. He starts by running 20 miles in the first week, and each subsequent week he increases his miles by 5%, which means he runs 105% of the previous week's mileage. The mileage for each week can be calculated as follows: - Week 1: \( 20 \) - Week 2: \( 20 \times (1 + 0.05) = 20 \times 1.05 = 21 \) - Week 3: \( 21 \times 1.05 = 21 \times 1.05 = 22.05 \) Continuing this, the number of miles run in week \( n \) can be expressed as: \[ \text{Miles in week } n = 20 \times (1.05)^{n-1} \] To find the total miles Suav runs over the 25 weeks, we calculate the sum of the geometric series: \[ S_n = a \frac{(1 - r^n)}{(1 - r)} \] Where: - \( a = 20 \) (the first term), - \( r = 1.05 \) (the common ratio), - \( n = 25 \). Calculating it: \[ S_{25} = 20 \frac{(1 - 1.05^{25})}{(1 - 1.05)} \] Now, let's calculate \( 1.05^{25} \): \[ 1.05^{25} \approx 3.386 \] Substituting this back in: \[ S_{25} = 20 \frac{(1 - 3.386)}{-0.05} = 20 \frac{-2.386}{-0.05} = 20 \times 47.72 = 954.4 \] Rounding to the nearest whole number, Suav would have run approximately **954 miles** over the 25 weeks.