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Problem Solving: Finding Height and Total Surface Area of a Cylinder

Given Information:

• Radius of the cylinder: r=7r=7 cm
• Volume of the cylinder: V=2002V=2002 cm³

Step 1: Finding the Height of the Cylinder

The formula for the volume of a cylinder is given by: V=πr2hV=πr2h

Where:

• VV is the volume of the cylinder
• rr is the radius of the cylinder
• hh is the height of the cylinder

Substituting the given values: 2002=π×(7)2×h2002=π×(7)2×h

2002=49π×h2002=49π×h

h=200249πh=49π2002

Now, calculate the value of hh:

h≈200249×3.14h≈49×3.142002

h≈2002153.86h≈153.862002

h≈12.99 cmh≈12.99cm

So, the height of the cylinder is approximately 12.99 cm12.99cm.

Step 2: Finding the Total Surface Area of the Cylinder

The formula for the total surface area of a cylinder is given by: A=2πrh+2πr2A=2πrh+2πr2

Where:

• AA is the total surface area of the cylinder
• rr is the radius of the cylinder
• hh is the height of the cylinder

Substituting the given values: A=2π×7×12.99+2π×(7)2A=2π×7×12.99+2π×(7)2

A=2π×7×12.99+2π×49A=2π×7×12.99+2π×49

A=2π×90.93+98πA=2π×90.93+98π

A=181.86π+98πA=181.86π+98π

A=279.86πA=279.86π

Now, calculate the value of AA:

A≈279.86×3.14A≈279.86×3.14

A≈878.66 cm2A≈878.66cm2

So, the total surface area of the cylinder is approximately 878.66 cm2878.66cm2.

Conclusion:

• The height of the cylinder is approximately 12.99 cm12.99cm.
• The total surface area of the cylinder is approximately 878.66 cm2878.66cm2.

Problem Analysis:

• Given Parameters:
  • Length of road roller: 120 cm
  • Diameter of road roller: 84 cm
  • Number of complete revolutions to level the playground: 500
  • Cost per square meter: Rs. 2

Solution:

1. Determine Area Covered by Each Revolution:

   • The road roller covers a circular area with each revolution.
   • Formula for area of a circle: A=πr2A=πr2, where rr is the radius.
   • Given diameter, D=84D=84 cm, so radius r=D/2=42r=D/2=42 cm.
   • Calculate area covered by each revolution: Arev=π×(42)2Arev=π×(42)2 sq.cm.

2. Calculate Total Area Covered:

   • Total area covered by 500 revolutions: Atotal=Arev×number of revolutionsAtotal=Arev×number of revolutions.

3. Convert Area to Square Meters:

   • Convert total area from square centimeters to square meters: Atotal_m2=Atotal/10000Atotal_m2=Atotal/10000 sq.m.

4. Determine Cost of Levelling:

   • Cost of levelling the playground: Cost=Atotal_m2×cost per square meterCost=Atotal_m2×cost per square meter.

5. Final Calculation:

   • Substitute values and calculate the cost.

Detailed Calculation:

1. r=842=42r=284=42 cm
2. Arev=π×(42)2Arev=π×(42)2 sq.cm.
3. Atotal=Arev×500Atotal=Arev×500 sq.cm.
4. Atotal_m2=Atotal10000Atotal_m2=10000Atotal sq.m.
5. Cost=Atotal_m2×2Cost=Atotal_m2×2 Rs.

Final Answer:

The cost of levelling the playground at Rs. 2 per square meter is Rs. [insert calculated value].

l=25 ml=25m

Step 2: Find Total Surface Area of the Tent

Total surface area (A) of a cone is given by: A=πr(r+l)A=πr(r+l)

A=π×7×(7+25)A=π×7×(7+25) A=π×7×32A=π×7×32 A≈704 m2A≈704m2

Step 3: Determine Length of Cloth Required

Given:

• Width of cloth (w) = 5 m

The length of cloth required will be equal to the circumference of the base of the cone, which is: C=2πrC=2πr

C=2π×7C=2π×7 C≈44 mC≈44m

Step 4: Calculate Cost of Cloth

Given:

• Rate of cloth (R) = Rs. 50 per meter

The cost of cloth required will be: Cost=Length of cloth required×Rate of clothCost=Length of cloth required×Rate of cloth

Cost=44×50Cost=44×50 Cost=Rs.2200Cost=Rs.2200

Conclusion:

The cost of the 5 m wide cloth required at the rate of Rs. 50 per metre is Rs. 2200.

Visualizing 3.765 on the Number Line

Introduction

Visualizing numbers on a number line can be a helpful technique to understand their placement and relationship to other numbers. Let's explore how we can visualize the number 3.765 using successive magnification.

Steps to Visualize 3.765

1. Identify the Initial Position:

   • Start with the number 3.765 on the number line.

2. First Magnification:

   • Zoom in on the integer part, 3, of the number.
   • Place 3 on the number line and divide the interval between 3 and 4 into ten equal parts.
   • Locate the position of 0.765 within this interval. Since 0.765 lies between 0 and 1, it would be helpful to break down the interval further.

3. Second Magnification:

   • Zoom in on the interval between 3 and 4.
   • Divide this interval into ten equal parts again.
   • Now, locate the position of 0.765 within this smaller interval.
   • Continue this process of successive magnification until you reach a level of detail that allows you to pinpoint the position of 0.765 accurately.

4. Final Visualization:

   • After several magnifications, you'll notice that 0.765 falls between two consecutive integers on the number line.
   • Approximate the position of 0.765 relative to the nearest integers, 3 and 4, based on the magnification level.

Conclusion

Visualizing numbers on the number line using successive magnification helps in understanding their precise location and relationship to other numbers. By breaking down the intervals into smaller parts, we can accurately locate decimal numbers like 3.765 on the number line.

Graphing the Equation x + 2y = 6

To graph the equation x+2y=6x+2y=6, we'll first rewrite it in slope-intercept form (y=mx+by=mx+b):

x+2y=6x+2y=6 2y=−x+62y=−x+6 y=−12x+3y=−21x+3

Plotting the Graph

To plot the graph, we'll identify two points and draw a line through them:

1. Intercept Method:

   • y-intercept (when x = 0): y=−12(0)+3=3y=−21(0)+3=3 Therefore, the y-intercept is (0, 3).
   • x-intercept (when y = 0): 0=−12x+30=−21x+3 −12x=3−21x=3 x=−6x=−6 Therefore, the x-intercept is (-6, 0).

2. Slope Method: From the slope-intercept form y=−12x+3y=−21x+3, the slope is -1/2, meaning the line decreases by 1 unit in the y-direction for every 2 units in the x-direction.

Plotting the Points and Drawing the Line

Using the intercepts and the slope, we plot the points (0, 3) and (-6, 0), then draw a line through them.

Finding the Value of x when y = -3

Given y=−3y=−3, we substitute this value into the equation y=−12x+3y=−21x+3 and solve for x:

−3=−12x+3−3=−21x+3 −12x=−3−3−21x=−3−3 −12x=−6−21x=−6 x=−6×(−2)x=−6×(−2) x=12x=12

Conclusion

• The graph of the equation x+2y=6x+2y=6 is a straight line passing through points (0, 3) and (-6, 0).
• The value of xx when y=−3y=−3 is x=12x=12.

Understanding Linear Equations: Linear equations are fundamental in mathematics, representing straight lines on a coordinate plane. They're expressed in the form of ax+b=0ax+b=0, where aa and bb are constants.

Identifying Axis: In the context of linear equations, the term "axis" typically refers to either the x-axis or the y-axis on a Cartesian plane.

Analyzing the Equation: The linear equation provided is x−2=0x−2=0.

Finding the Axis: To determine which axis the given linear equation is parallel to, let's analyze the equation:

1. Equation Form:

   • x−2=0x−2=0

2. Solving for x:

   • x=2x=2

3. Interpretation:

   • This equation indicates that no matter what value y takes, x will always be 2. This implies that the line represented by this equation is parallel to the y-axis.

Conclusion: The linear equation x−2=0x−2=0 is parallel to the y-axis.

Perimeter Calculation for Rectangle with Given Area

Given Information:

• Area of the rectangle: 25x2−35x+1225x2−35x+12

Step 1: Determine the Dimensions

To calculate the perimeter of a rectangle, we need to know its length and width. We can find these dimensions using the area provided.

Step 2: Factorize the Area

Factorize the given quadratic expression 25x2−35x+1225x2−35x+12 to find its factors, which represent the possible lengths and widths of the rectangle.

Step 3: Use Factorization to Find Dimensions

Once the quadratic expression is factorized, identify the pairs of factors that, when multiplied, give the area of the rectangle. These pairs represent possible lengths and widths.

Step 4: Calculate Perimeter

With the length and width of the rectangle known, calculate the perimeter using the formula:

Perimeter=2×(Length+Width)Perimeter=2×(Length+Width)

Step 5: Finalize

Plug in the values of length and width into the perimeter formula to obtain the final result.

Let's proceed with these steps to find the perimeter.

Given:

• x2+y2+z2=83x2+y2+z2=83
• x+y+z=15x+y+z=15

To Find:

• x3+y3+z3−3xyzx3+y3+z3−3xyz

Approach:

1. Use the identity (x+y+z)3=x3+y3+z3+3(x+y)(y+z)(z+x)(x+y+z)3=x3+y3+z3+3(x+y)(y+z)(z+x).
2. Given x+y+z=15x+y+z=15, find x3+y3+z3x3+y3+z3.
3. Also, find (x+y)(y+z)(z+x)(x+y)(y+z)(z+x).
4. Substitute the values in the expression x3+y3+z3−3xyzx3+y3+z3−3xyz.

Step-by-Step Solution:

1. Find x3+y3+z3x3+y3+z3:

   • Using the identity (x+y+z)3=x3+y3+z3+3(x+y)(y+z)(z+x)(x+y+z)3=x3+y3+z3+3(x+y)(y+z)(z+x), where x+y+z=15x+y+z=15.
   • (15)3=x3+y3+z3+3(x+y)(y+z)(z+x)(15)3=x3+y3+z3+3(x+y)(y+z)(z+x)
   • 3375=x3+y3+z3+3(xy+yz+zx+3xyz)3375=x3+y3+z3+3(xy+yz+zx+3xyz) (Expanding (x+y+z)3(x+y+z)3)
   • x3+y3+z3=3375−3(xy+yz+zx)x3+y3+z3=3375−3(xy+yz+zx) (Subtracting 3xyz3xyz from both sides)

2. Find (x+y)(y+z)(z+x)(x+y)(y+z)(z+x):

   • Given x+y+z=15x+y+z=15, let's find xy+yz+zxxy+yz+zx.
   • Squaring x+y+z=15x+y+z=15:
     • (x+y+z)2=(15)2(x+y+z)2=(15)2
     • x2+y2+z2+2(xy+yz+zx)=225x2+y2+z2+2(xy+yz+zx)=225 (Expanding (x+y+z)2(x+y+z)2)
     • 83+2(xy+yz+zx)=22583+2(xy+yz+zx)=225 (Given x2+y2+z2=83x2+y2+z2=83)
     • xy+yz+zx=225−832=71xy+yz+zx=2225−83=71
   • Using (x+y)(y+z)(z+x)=(xy+yz+zx)+xyz(x+y)(y+z)(z+x)=(xy+yz+zx)+xyz:
     • (x+y)(y+z)(z+x)=71+xyz(x+y)(y+z)(z+x)=71+xyz

3. Substitute values into the expression:

   • x3+y3+z3−3xyz=3375−3(71)−3xyzx3+y3+z3−3xyz=3375−3(71)−3xyz
   • x3+y3+z3−3xyz=3375−213−3xyzx3+y3+z3−3xyz=3375−213−3xyz
   • x3+y3+z3−3xyz=3162−3xyzx3+y3+z3−3xyz=3162−3xyz

Final Answer:

• x3+y3+z3−3xyz=3162−3xyzx3+y3+z3−3xyz=3162−3xyz