Nakeisha just started a running plan where she runs 7 miles the first week and then increases the number of miles she runs by 10% each week. If she keeps up this plan for 25 weeks, how many total miles would Nakeisha have run, to the nearest whole number?Answer:
Q. Nakeisha just started a running plan where she runs 7 miles the first week and then increases the number of miles she runs by 10% each week. If she keeps up this plan for 25 weeks, how many total miles would Nakeisha have run, to the nearest whole number?Answer:
Identify initial amount and rate: Identify the initial amount of miles and the rate of increase.Nakeisha starts with 7 miles in the first week and increases her running distance by 10% each week.Initial miles (a)=7Rate of increase (r)=10% or 0.10
Calculate total miles per week: Calculate the total miles run for each week.The total miles run in each subsequent week can be calculated using the formula for the nth term of a geometric sequence:Week n miles = a×(1+r)(n−1)We will use this formula to calculate the miles run each week and then sum them up for 25 weeks.
Calculate total miles over 25 weeks: Calculate the total miles run over 25 weeks.We need to sum up the miles for each week from week 1 to week 25.Total miles = a+a(1+r)+a(1+r)2+…+a(1+r)25−1This is the sum of a finite geometric series.
Use formula for sum of series: Use the formula for the sum of a finite geometric series.The sum S of the first n terms of a geometric series is given by:S=a×1−(1+r)1−(1+r)nWe will substitute n=25, a=7, and r=0.10 into this formula to find the total miles.
Perform calculation using formula: Perform the calculation using the formula.S=7×(1−(1+0.10)25)/(1−(1+0.10))S=7×(1−(1.10)25)/(1−1.10)S=7×(1−(1.10)25)/(−0.10)
Calculate exact total and round: Calculate the exact total and then round to the nearest whole number.First, calculate (1.10)25, then substitute it back into the formula to find S.After finding S, round it to the nearest whole number.
Use calculator to find total: Use a calculator to find (1.10)25 and then find S.(1.10)25≈10.834705...S≈7×(1−10.834705...)/(−0.10)S≈7×(−9.834705...)/(−0.10)S≈7×98.34705...S≈688.42935...Rounded to the nearest whole number, S≈688 miles.
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