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There is a question in my Pure Maths book which seems to confuse me. Ive done the rest but somehow this question seems to confuse me I think enough info is not given.

A water tank has a rectangular base 1.5m by 1.2m. The sides are vertical and water is being added to the tank at a constant rate of 0.45m^3 per minute. At what rate is the depth of water in the tank increasing?

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You don't need calculus for this.

Every minute $0.45 \text{ m}^3$ of water is added. Since $1.5\times1.2 \text{ m}^2$ is the area of the base, $0.45 \text{ m}^3$ of water will have height $\dfrac{0.45 \text{ m}^3}{1.5\times1.2 \text{ m}^2}=0.25 \text{ m}$. Thus the required rate is $0.25 \text{ m min}^{-1}$.

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    $\begingroup$ @Manny264: The "big picture" reason you don't need calculus for this is because the volume and height have a linear relationship. When the relationship becomes nonlinear, calculus helps for the same reason that calculus helps analyze curves. $\endgroup$ Oct 5 '13 at 14:08
  • $\begingroup$ Im getting u there but being so much into calculus these past few months when i came across this i was so very stumbled like whats going on...i still need to make a logical explanation to myself im trying to get the relationship right. So as volume of water is added height increases which is connected by the base area right? $\endgroup$
    – Manny265
    Oct 5 '13 at 15:39

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