Mathematics, 30.12.2020 22:00 genyjoannerubiera

A block of ice has a square top and bottom and rectangular sides. At a certain point in time, the square top and bottom each have a length of 30 cm, which are decreasing at a
rate of 2 cm/h. At the same time, the height of the ice block is 20 cm and decreasing at
3 cm/h. How fast is the ice melting?

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Answer from: alinadancer2717

$\frac{dV}{dt} = 360 \ cm^3/h$

General Formulas and Concepts:

Pre-Algebra

Order of Operations: BPEMDAS

Brackets Parenthesis Exponents Multiplication Division Addition Subtraction Left to Right

Equality Properties

Geometry

Volume of a Rectangular Prism: V = lwh

Calculus

Derivatives

Derivative Notation

Differentiating with respect to time

Basic Power Rule:

f(x) = cxⁿ f’(x) = c·nxⁿ⁻¹

Step-by-step explanation:

Step 1: Define

$l = 30 \ cm\\w = l\\\frac{dl}{dt} = 2 \ cm/h\\h = 20 \ cm\\\frac{dh}{dt} = 3 \ cm/h$

Step 2: Differentiate

Rewrite [VRP]: V = l^2h

Differentiate [Basic Power Rule]: $\frac{dV}{dt} = 2l\frac{dl}{dt} \frac{dh}{dt}$

Step 3: Solve for Rate

Substitute: $\frac{dV}{dt} = 2(30 \ cm)(2 \ cm/h)(3 \ cm/h)$ Multiply: $\frac{dV}{dt} = 360 \ cm^3/h$

Here this tells us that our volume is decreasing (ice melting) at a rate of 360 cm³ per hour.

Answer from: Quest

v = 1/3 a^2h

step-by-step explanation:

the volume is 1/3 a^2h.

Answer from: Quest

third choice down

step-by-step explanation:

the first inequality is based on the number of adults and campers, and the second inequality is based on the cost of feeding both the adult and the camper.

we know that there is room for 525 people max. it's ok to have less than 525, but it's not ok to have more than 525, so the inequality is less than or equal to. the number combination of adults (x) and campers (y) cannot exceed this 525 max. therefore:

x + y ≤ 525

now we talk about cost. it costs $9 to feed one adult, so depending upon the number of adults you have (x) depends upon how much it will cost to feed that number of adults. same with the campers, who cost $5 to feed. the adults can be represented by 9x and the campers can be represented by 5y. since the budget cannot exceed 1,200, the second inequality is:

9x + 5y ≤ 1200

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