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Water is flowing into and being removed from a tank - Leaving Cert Mathematics - Question 10(a) - 2021

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Question 10(a)

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Water is flowing into and being removed from a tank. The volume of water in the tank is measured on a daily basis, starting at day 0. The volume of water, in litres,... show full transcript

Worked Solution & Example Answer:Water is flowing into and being removed from a tank - Leaving Cert Mathematics - Question 10(a) - 2021

Step 1

Find the value of $t$ when the tank empties.

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Answer

To find when the tank empties, we need to set the volume function to zero:

This simplifies to:

Factoring out tt, we get:

Thus, t=0t = 0 or t=101333.67t = \frac{101}{3} \approx 33.67 days. Since t0t \geq 0, the tank empties when t33.67t \approx 33.67 days.

Step 2

Find the rate at which the volume of water in the tank is changing when $t = 5$.

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Answer

To find the rate of change, we need to first calculate the derivative of the volume function:

Now, substituting t=5t = 5 into the derivative:

Thus, at t=5t = 5, the volume of water in the tank is changing at a rate of 71 litres per day.

Step 3

Find the value of $t$ when the volume of water in the tank is a maximum.

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Answer

To find the maximum volume, we set the derivative to zero:

Rearranging gives:

Therefore, the volume of water is maximized at approximately t=16.83t = 16.83 days.

Step 4

Find the maximum volume of the water in the tank, correct to the nearest litre.

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Answer

To find the maximum volume, substitute t16.83t \approx 16.83 back into the original volume function:

Calculating this gives:

1000.80+690.03848.97841.86.\approx 1000.80 + 690.03 - 848.97\newline \approx 841.86.\newline

Hence, the maximum volume of the water in the tank is approximately 842 litres.

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