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The side length of a square is increasing at a rate of 15 millimeters per second.
At a certain instant, the side length is 22 millimeters.
What is the rate of change of the area of the square at that instant (in square millimeters per second)?
Choose 1 answer:
(A) 660
(B) 484
(C) 30
(D) 225

The side length of a square is increasing at a rate of 1515 millimeters per second.\newlineAt a certain instant, the side length is 2222 millimeters.\newlineWhat is the rate of change of the area of the square at that instant (in square millimeters per second)?\newlineChoose 11 answer:\newline(A) 660660\newline(B) 484484\newline(C) 3030\newline(D) 225225

Full solution

Q. The side length of a square is increasing at a rate of 1515 millimeters per second.\newlineAt a certain instant, the side length is 2222 millimeters.\newlineWhat is the rate of change of the area of the square at that instant (in square millimeters per second)?\newlineChoose 11 answer:\newline(A) 660660\newline(B) 484484\newline(C) 3030\newline(D) 225225
  1. Find Area Formula: First, let's find the formula for the area of a square, which is side length squared s2s^2.
  2. Derivative of Area: Now, we need to find the derivative of the area with respect to time dAdt\frac{dA}{dt} since we're looking for the rate of change of the area.
  3. Derivative of s2s^2: The derivative of s2s^2 with respect to time (dsdt\frac{ds}{dt}) is 2sdsdt2s \cdot \frac{ds}{dt}, where dsdt\frac{ds}{dt} is the rate of change of the side length.
  4. Plug in Values: Plug in the values: s=22mms = 22\,\text{mm} and dsdt=15mm/s\frac{ds}{dt} = 15\,\text{mm/s}. So, dAdt=2×22mm×15mm/s\frac{dA}{dt} = 2 \times 22\,\text{mm} \times 15\,\text{mm/s}.
  5. Calculate Rate of Change: Calculate the rate of change of the area: dAdt=2×22×15=660mm2/s.\frac{dA}{dt} = 2 \times 22 \times 15 = 660 \, \text{mm}^2/\text{s}.

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