document.write( "Question 544013: Mary saves $20 the first week. She saves an additional 10% each week. How much will she save on the seventh week? \n" ); document.write( "
Algebra.Com's Answer #355045 by jpg7n16(66)\"\" \"About 
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Well since we're trying to find how much she saves each week, let's look to see what pattern forms:
\n" ); document.write( "\"Week1+=+20\"
\n" ); document.write( "\"Week2+=+20%2A1.10+=+22\"
\n" ); document.write( "\"Week3+=+22%2A1.10+=+%2820%2A1.10%29%2A1.10+=+20%2A%281.10%5E2%29+=+24.20\"
\n" ); document.write( "\"Week4+=+24.20%2A1.10+=+%2820%2A1.10%2A1.10%29%2A1.10+=+20%2A%281.10%5E3%29+=+26.62\"
\n" ); document.write( "Have you spotted the pattern yet? It's always \"20%2A%281.10%5Ex%29\" where the exponent is always the # of the week, minus 1. (Week2 was \"20%2A%281.10%5E1%29\")
\n" ); document.write( ".
\n" ); document.write( "So use the following formula:
\n" ); document.write( "\"A=p%2A%281.10%29%5E%28n-1%29\"
\n" ); document.write( "\"A\" = amount saved
\n" ); document.write( "\"p\" = initial amount
\n" ); document.write( "\"n\" = number of weeks
\n" ); document.write( ".
\n" ); document.write( "So for instance, week 1:
\n" ); document.write( "\"A=p%2A%281.10%29%5E%28n-1%29\"
\n" ); document.write( "\"A=20%2A%281.10%29%5E%281-1%29\"
\n" ); document.write( "\"A=20%2A%281.10%29%5E%280%29=20%2A1=20\"
\n" ); document.write( ".
\n" ); document.write( "Or week 4:
\n" ); document.write( "\"A=p%2A%281.10%29%5E%28n-1%29\"
\n" ); document.write( "\"A=20%2A%281.10%29%5E%284-1%29\"
\n" ); document.write( "\"A=20%2A%281.10%29%5E%283%29=20%2A1.331=26.62\"
\n" ); document.write( ".
\n" ); document.write( "Both of which we know to be true from our examples above. But now you know how to calculate week 7, 17, or 700 (if needed). Hope this helps! \n" ); document.write( "
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