Math Chapter: Percentages and Measures

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Questions and Answers

What is the volume of a rectangular prism with dimensions 2 cm, 4 cm, and 5 cm?

  • 40 cm³ (correct)
  • 50 cm³
  • 30 cm³
  • 60 cm³

Pressure can be calculated by multiplying force and area.

False (B)

What is the formula for pressure?

Pressure = Force ÷ Area

To convert 8 km/h to mph, you multiply by ______ miles.

<p>1.6</p> Signup and view all the answers

If a force of 10 Newtons is applied to an area of 20 cm², what is the pressure produced?

<p>0.5 N/cm² (B)</p> Signup and view all the answers

Define direct proportion.

<p>Two sets of values are in direct proportion if they have a common multiplier.</p> Signup and view all the answers

The formula for y in terms of x when y is in direct proportion to x is y = ______ x.

<p>k</p> Signup and view all the answers

Match the following conversions:

<p>8 km/h = 5 mph 70 mph = 31.29 m/s 1 km = 0.621 miles 18 km/h = 0.005 m/s</p> Signup and view all the answers

What is the multiplier to increase an amount by 12%?

<p>1.12 (C)</p> Signup and view all the answers

If you increase an amount by 10% and then by another 12%, the overall percentage increase is 122%.

<p>False (B)</p> Signup and view all the answers

Calculate the density of a piece of metal that weighs 40g and has a volume of 4cm³.

<p>10 g/cm³</p> Signup and view all the answers

Speed is calculated using the formula __________.

<p>Distance ÷ Time</p> Signup and view all the answers

Match the following measurements with their formulas:

<p>Speed = Distance ÷ Time Density = Mass ÷ Volume Volume = Length × Width × Height Time = Distance ÷ Speed</p> Signup and view all the answers

A block of ice measures 5 cm by 2 cm by 4 cm. What is the volume of the cube?

<p>40 cm³ (C)</p> Signup and view all the answers

To find the mass of an object, you can multiply its density by its volume.

<p>True (A)</p> Signup and view all the answers

To convert 45 minutes into hours, you would write it as __________.

<p>0.75</p> Signup and view all the answers

What is the equation for y in terms of x when y is proportional to $x^2$?

<p>y = 4x^2 (B)</p> Signup and view all the answers

In direct proportion, if one value increases, the other value must increase as well.

<p>True (A)</p> Signup and view all the answers

What is the value of k when x = 4 and y = 25 in an inverse proportion scenario?

<p>100</p> Signup and view all the answers

The multiplier in the inverse proportion relationship is represented by _____ .

<p>k</p> Signup and view all the answers

Match the following equations with their type of proportion:

<p>y = kx^2 = Direct Proportion y = k/x = Inverse Proportion g = k√f = Direct Proportion k = yx = Inverse Proportion</p> Signup and view all the answers

When f = 9 and g = 30, how can g be expressed in terms of f?

<p>g = k√f (D)</p> Signup and view all the answers

If y and x are inversely proportional, then when x increases, y must also increase.

<p>False (B)</p> Signup and view all the answers

If x = 2, find the value of y given that k = 100 and y is inversely proportional to x.

<p>50</p> Signup and view all the answers

Flashcards

Pressure

The amount of force applied per unit area.

Force

The ability to change the motion of an object.

Volume

The space occupied by an object.

Density

The mass per unit volume of a substance.

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Direct Proportion

Two sets of values are directly proportional if they have a common multiplier.

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Direct Proportion Formula

The relationship between two variables where the ratio between them is constant.

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Converting Measurements

The process of converting units from one system to another.

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Speed

A unit representing the rate of change of distance over time.

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Percentage Increase

Increasing a value by a specific percentage.

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Multiplier

A number that represents the percentage increase as a decimal.

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Overall Percentage Increase

The overall increase in percentage after applying multiple percentage increases sequentially.

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Compound Measure

A measure that combines two different units, like speed (distance over time).

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Mass

The total amount of matter in an object, measured in grams or kilograms.

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Multiplier in Direct Proportion

The constant of proportionality in a direct proportion relationship. It represents the factor by which one variable changes when the other variable changes by one unit.

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Inverse Proportion

Two sets of values are inversely proportional if one value increases as the other decreases, maintaining a constant product.

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Inverse Proportion Formula

The equation relating two inversely proportional variables y and x, where their product is constant and represented by k. The equation is often written as yx = k.

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Multiplier in Inverse Proportion

The constant of proportionality in an inverse proportion relationship. It represents the unchanging product of the two inversely proportional variables.

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Writing an Equation in Direct Proportion

A common technique used to write equations using direct proportion in the form of y = kx. This involves finding the value of k using a given pair of values for y and x.

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Writing an Equation in Inverse Proportion

A common technique used to write equations using inverse proportion in the form of yx = k. This involves finding the value of k using a given pair of values for y and x.

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Study Notes

Repeated Percentages

  • To increase a value by 10%, multiply by 1.10
  • To increase a value by 12%, multiply by 1.12
  • To find the overall percentage increase from multiple percentage increases, multiply the individual multipliers together

Compound Percentages

  • Compound Interest: Calculate the future value of an amount that earns interest over time, where the interest is added to the principal each period.
    • Formula: Amount x (Multiplier)^Time
  • Compound Depreciation: Calculate the future value of an amount that loses value over time, where the depreciation is subtracted from the principal each period.
    • Formula: Amount x (Decreasing Multiplier)^Time

Compound Measures

  • Compound measures combine two or more units of measurement
  • Density: Mass / Volume. Measured in g/cm³, kg/m³ or kg/l
  • Speed: Distance / Time. Units include m/s, km/h or mph
  • Pressure: Force / Area. Units include N/m² or N/cm²
  • Fuel Consumption: Distance / Volume. Units include km/l or mpg

Compound Measure - Speed

  • Speed = Distance / Time
  • Time = Distance / Speed
  • Distance = Speed x Time
  • Convert minutes to hours to calculate speed

Compound Measure - Density

  • Density = Mass / Volume
  • Volume = Mass / Density
  • Mass = Density x Volume
  • Used to determine how tightly matter is packed within a given volume

Compound Measure - Pressure

  • Pressure = Force / Area
  • Area = Force / Pressure
  • Force = Pressure x Area
  • Measured in N/m², N/cm², N/km²

Compound Measure - Converting Measurements

  • Conversion factors will vary
  • Examples include converting km/h to mph, km/h to km/s, and mph to m/s

What is Direct Proportion?

  • Two sets of values are in direct proportion if they have a common multiplier.
  • Direct proportion graphs are straight lines that pass through the origin (0,0).

Direct Proportion - without powers

  • If y is directly proportional to x, then y = kx, where k is the constant of proportionality (multiplier).
  • Find the multiplier (k) by dividing a y value by its corresponding x value.
  • Use the multiplier (k) to generate more calculations for the same relationship.

Direct Proportion - with powers

  • If y is directly proportional to x², then y = kx².
  • If y is directly proportional to x³, then y = kx³.

Inverse Proportion

  • Two sets of values are inversely proportional if one value increases while the other decreases at the same rate.
  • To write an equation for inverse proportionality: y= k/x where k is the constant of proportionality (k = yx).

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