Chapter 8: Infinite Sequences and Series
Section 8.2: Series
Example 8.2.10
Write the repeating decimal 7.435&conjugate0; as the ratio of two integers.
Solution
Mathematical Solution
To implement the simple approach expounded in Example 8.2.9, call the given number M so that 10 M=74.35&conjugate0;. Then S=0.35&conjugate0; and 100 S=35.35&conjugate0; and S=35/99. Hence, 10 M=74+35/99, and
M=74/10+35/990=7361990
To obtain this same result by summing a geometric series, write the given repeating decimal as
7.435&conjugate0;
=7.4+.035+.00035+⋯
=7410+35103+35105+⋯
=7410+351031+10−2+10−4+⋯
=7410+35103∑n=0∞1102n
=7410+3510311−1/100
=7410+3510310099
=7410+35990
=7361990
Maple Solution
Enter the series representation of the given number.
Context Panel: Evaluate and Display Inline
7410+35103∑n=0∞1102n = 7361990
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