This problem involves finding the time it takes for multiple pipes operating simultaneously to fill a tank, given their individual filling times.
First, determine the rate at which each pipe fills the tank. The rate is the fraction of the tank filled per hour.
To find the combined rate when all pipes operate together, add their individual rates.
Combined Rate = Rate A + Rate B + Rate C
Combined Rate = $\frac{1}{19} + \frac{1}{21} + \frac{1}{8}$
Find a common denominator, which is the least common multiple (LCM) of 19, 21, and 8. LCM(19, 21, 8) = $19 \times 21 \times 8 = 3192$.
Combined Rate = $\frac{1 \times (21 \times 8)}{19 \times 21 \times 8} + \frac{1 \times (19 \times 8)}{19 \times 21 \times 8} + \frac{1 \times (19 \times 21)}{19 \times 21 \times 8}$
Combined Rate = $\frac{168}{3192} + \frac{152}{3192} + \frac{399}{3192}$
Combined Rate = $\frac{168 + 152 + 399}{3192} = \frac{719}{3192}$ tank per hour.
The time taken to fill the tank together is the reciprocal of the combined rate.
Time = $\frac{1}{\text{Combined Rate}}$
Time = $\frac{1}{\frac{719}{3192}} = \frac{3192}{719}$ hours.
Convert the improper fraction $\frac{3192}{719}$ into a mixed number.
Divide 3192 by 719:
$3192 \div 719 = 4$ with a remainder of $3192 - (4 \times 719) = 3192 - 2876 = 316$.
Therefore, the time taken is $4 \frac{316}{719}$ hours.
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