A reservoir will be filled in 12 hours if two pipes function simultan...
Let the first pipe fill the reservoir in x hours.
Then, the second pipe can fill the reservoir in x – 10 hours.
Now, according to the question,
1/x + 1/(x-10) = 1/12
⇒ 12(x – 10 + x) = x2 – 10x
⇒24x – 120 = x2 – 10x
⇒x2 – 34x + 120 = 0
⇒x2 – 30x - 4x + 120 = 0
⇒(x – 30)(x – 4) = 0
⇒x = 30, 4
But, x ≠ 4 (∵ x – 10 should be positive)
∴ x = 30 hours
x – 10 = 20 hours
A reservoir will be filled in 12 hours if two pipes function simultan...
Let's assume that the first pipe can fill the reservoir in x hours.
Given that the second pipe fills the reservoir 10 hours faster than the first pipe, the second pipe can fill the reservoir in (x - 10) hours.
To find the time taken by both pipes working together, we can use the concept of rates. The rate at which the first pipe fills the reservoir is 1/x (as it fills the reservoir in x hours), and the rate at which the second pipe fills the reservoir is 1/(x - 10) (as it fills the reservoir in x - 10 hours).
When both pipes work simultaneously, their rates add up. So, the combined rate of both pipes is 1/x + 1/(x - 10).
The reservoir will be filled in 12 hours when both pipes work simultaneously. So, the combined rate of both pipes is 1/12.
Therefore, we can write the equation as:
1/x + 1/(x - 10) = 1/12
To solve this equation, we can multiply through by the common denominator, which is 12x(x - 10):
12(x - 10) + 12x = x(x - 10)
Expanding and simplifying the equation:
12x - 120 + 12x = x^2 - 10x
24x - 120 = x^2 - 10x
Rearranging the equation and setting it equal to zero:
x^2 - 34x + 120 = 0
Factoring the quadratic equation:
(x - 20)(x - 6) = 0
Solving for x, we get two possible solutions: x = 20 and x = 6.
Since the second pipe takes 10 hours less than the first pipe, the second pipe cannot take more time than the first pipe. Therefore, we can eliminate x = 20 as a valid solution.
Hence, the first pipe takes 6 hours to fill the reservoir, and the second pipe takes 6 - 10 = -4 hours, which is not possible.
Therefore, the only valid solution is x = 6, which means the second pipe takes 6 - 10 = -4 hours.
Therefore, the second pipe takes 20 hours to fill the reservoir (Option D).
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