Questions: Wed Jan 1 74 CALCULUS AB Section II Part B: No calculator is allowed for these problems. t 0 2 5 9 13 15 --------------------- h'(t) 0.4 0.5 0.7 1.0 1.1 1.3 3. A tank with a rectangular base measuring 10 inches by 20 inches is being filled with water at a variable rate. The depth of the water in the tank is given by a twice-differentiable function h of time, t, measured in minutes. The table above gives the rate of change, h'(t), of the depth of the water in the tank for selected values of t over the time interval 0 ≤ t ≤ 15. During this interval h''(t)>0. When t=5 minutes, the depth of the water is 6 inches. (Note: The volume of the water in the tank is given by V=lwh.) (a) Approximate the depth of the water in the tank at t=4 minutes using the tangent line approximation at t=5. Is your estimate greater than or less than the true value? Give a reason for your answer. (b) Find the rate of change of the volume of the water in the tank at t=2 minutes. Indicate units of measure. (c) Use a left Riemann sum with five subintervals indicated by the table to approximate ∫ from 0 to 15 of h'(t) dt. Using correct units, explain the meaning of ∫ from 0 to 15 of h'(t) dt in terms of the depth of the water in the tank. (d) Is the approximation in part (c) greater than or less than ∫ from 0 to 15 of h'(t) dt? Give a reason for your answer.

Wed Jan 1

74 CALCULUS AB

Section II Part B: No calculator is allowed for these problems.

t  0  2  5  9  13  15
---------------------
h'(t)  0.4  0.5  0.7  1.0  1.1  1.3

3. A tank with a rectangular base measuring 10 inches by 20 inches is being filled with water at a variable rate. The depth of the water in the tank is given by a twice-differentiable function h of time, t, measured in minutes. The table above gives the rate of change, h'(t), of the depth of the water in the tank for selected values of t over the time interval 0 ≤ t ≤ 15. During this interval h''(t)>0. When t=5 minutes, the depth of the water is 6 inches.
(Note: The volume of the water in the tank is given by V=lwh.)
(a) Approximate the depth of the water in the tank at t=4 minutes using the tangent line approximation at t=5. Is your estimate greater than or less than the true value? Give a reason for your answer.
(b) Find the rate of change of the volume of the water in the tank at t=2 minutes. Indicate units of measure.
(c) Use a left Riemann sum with five subintervals indicated by the table to approximate ∫ from 0 to 15 of h'(t) dt. Using correct units, explain the meaning of ∫ from 0 to 15 of h'(t) dt in terms of the depth of the water in the tank.
(d) Is the approximation in part (c) greater than or less than ∫ from 0 to 15 of h'(t) dt? Give a reason for your answer.
Transcript text: Wed Jan 1 74 CALCULUS AB Section II Part B: No calculator is allowed for these problems. \begin{tabular}{|c|c|c|c|c|c|c|} \hline$t$ & 0 & 2 & 5 & 9 & 13 & 15 \\ \hline$h^{\prime}(t)$ & 0.4 & 0.5 & 0.7 & 1.0 & 1.1 & 1.3 \\ \hline \end{tabular} 3. A tank with a rectangular base measuring 10 inches by 20 inches is being filled with water at a variable rate. The depth of the water in the tank is given by a twice-differentiable function $h$ of time, $t$, measured in minutes. The table above gives the rate of change, $h^{\prime}(t)$, of the depth of the water in the tank for selected values of $t$ over the time interval $0 \leq t \leq 15$. During this interval $h^{\prime \prime}(t)>0$. When $t=5$ minutes, the depth of the water is 6 inches. (Note: The volume of the water in the tank is given by $V=l w h$.) (a) Approximate the depth of the water in the tank at $t=4$ minutes using the tangent line approximation at $t=5$. Is your estimate greater than or less than the true value? Give a reason for your answer. (b) Find the rate of change of the volume of the water in the tank at $t=2$ minutes. Indicate units of measure. (c) Use a left Riemann sum with five subintervals indicated by the table to approximate $\int_{0}^{15} h^{\prime}(t) d t$. Using correct units, explain the meaning of $\int_{0}^{15} h^{\prime}(t) d t$ in terms of the depth of the water in the tank. (d) Is the approximation in part (c) greater than or less than $\int_{0}^{15} h^{\prime}(t) d t$ ? Give a reason for your answer.
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Solution

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Solution Steps

Step 1: Approximate the Depth at t=4 t=4

To approximate the depth of the water in the tank at t=4 t=4 minutes using the tangent line approximation at t=5 t=5 , we use the formula: h(4)h(5)+h(5)(45) h(4) \approx h(5) + h'(5) \cdot (4 - 5) Substituting the known values: h(4)6+0.7(1)=60.7=5.3 h(4) \approx 6 + 0.7 \cdot (-1) = 6 - 0.7 = 5.3 Since h(t)>0 h''(t) > 0 indicates that h(t) h'(t) is increasing, the tangent line approximation will be less than the true value.

Step 2: Rate of Change of Volume at t=2 t=2

The rate of change of the volume of water in the tank at t=2 t=2 minutes is calculated as: dVdt=Ah(2) \frac{dV}{dt} = A \cdot h'(2) where A=10×20=200 A = 10 \times 20 = 200 square inches and h(2)=0.5 h'(2) = 0.5 : dVdt=2000.5=100.0 cubic inches per minute \frac{dV}{dt} = 200 \cdot 0.5 = 100.0 \text{ cubic inches per minute}

Step 3: Left Riemann Sum Approximation

To approximate 015h(t)dt\int_{0}^{15} h^{\prime}(t) \, dt using a left Riemann sum with the given data: 015h(t)dti=04h(ti)(ti+1ti) \int_{0}^{15} h^{\prime}(t) \, dt \approx \sum_{i=0}^{4} h'(t_i) \cdot (t_{i+1} - t_i) Calculating the left Riemann sum: 015h(t)dt(20)0.4+(52)0.5+(95)0.7+(139)1.0+(1513)1.1 \int_{0}^{15} h^{\prime}(t) \, dt \approx (2 - 0) \cdot 0.4 + (5 - 2) \cdot 0.5 + (9 - 5) \cdot 0.7 + (13 - 9) \cdot 1.0 + (15 - 13) \cdot 1.1 This results in: =20.4+30.5+40.7+41.0+21.1=0.8+1.5+2.8+4.0+2.2=11.3 = 2 \cdot 0.4 + 3 \cdot 0.5 + 4 \cdot 0.7 + 4 \cdot 1.0 + 2 \cdot 1.1 = 0.8 + 1.5 + 2.8 + 4.0 + 2.2 = 11.3 Thus, the left Riemann sum approximation is 9.1 9.1 cubic inches.

Final Answer

  • Approximate depth at t=4 t=4 : h(4)=5.3 \boxed{h(4) = 5.3}
  • Rate of change of volume at t=2 t=2 : dVdt=100.0 cubic inches per minute \boxed{\frac{dV}{dt} = 100.0 \text{ cubic inches per minute}}
  • Left Riemann sum approximation: 015h(t)dt9.1 \boxed{\int_{0}^{15} h^{\prime}(t) \, dt \approx 9.1}
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