Subjects algebra

Continued Fraction D568D5

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1. Problem: Given positive integers $a, b, c, d$ satisfy the equation $$a + \frac{1}{b + \frac{1}{c + \frac{1}{d}}} = \frac{23}{16}.$$ Find the value of $a + b + c + d$. 2. First, note that $a, b, c, d$ are positive integers and the expression is a continued fraction. 3. Since $a$ is an integer and the whole expression equals $\frac{23}{16} = 1 + \frac{7}{16}$, we try $a=1$ because $1 < \frac{23}{16} < 2$. 4. Substitute $a=1$: $$1 + \frac{1}{b + \frac{1}{c + \frac{1}{d}}} = \frac{23}{16} \implies \frac{1}{b + \frac{1}{c + \frac{1}{d}}} = \frac{23}{16} - 1 = \frac{7}{16}.$$ 5. Invert both sides: $$b + \frac{1}{c + \frac{1}{d}} = \frac{16}{7} = 2 + \frac{2}{7}.$$ Since $b$ is a positive integer, try $b=2$. 6. Substitute $b=2$: $$2 + \frac{1}{c + \frac{1}{d}} = \frac{16}{7} \implies \frac{1}{c + \frac{1}{d}} = \frac{16}{7} - 2 = \frac{16}{7} - \frac{14}{7} = \frac{2}{7}.$$ 7. Invert again: $$c + \frac{1}{d} = \frac{7}{2} = 3 + \frac{1}{2}.$$ Since $c$ is a positive integer, try $c=3$. 8. Substitute $c=3$: $$3 + \frac{1}{d} = \frac{7}{2} \implies \frac{1}{d} = \frac{7}{2} - 3 = \frac{7}{2} - \frac{6}{2} = \frac{1}{2}.$$ 9. Therefore, $d=2$. 10. Finally, sum all values: $$a + b + c + d = 1 + 2 + 3 + 2 = 8.$$ Answer: 8 (Option D).