Math Problem Statement

Q1. If the ratio of the areas of two squares is 49:169, then find the ratio of their perimeters. a. 7:11 b. 13:9 c. 12:13 d. 28:52 Q2. A cuboid 16m long, 14 m broad and 7 m high. Which of the following statements is correct? a. The volume of the cuboid is 1568 cubic meters. b. The lateral surface area is 420 sq. meters. c. The ratio of the volume and LSA is 392:105 d. All of the above Q3. Find the length of the longest pole that can be placed in a room 12 m long, 8m broad and 9 m high. A) 16 m B) 17 m C) 18 m D) 19 m Q4. If the volume of a sphere is divided by its surface area, the answer obtained is 27cm. Find the diameter of the sphere. a. 122cm b. 81cm c. 162cm d. 44cm Q5. Find the height of a cylinder whose radius is 7 cm and the total surface area is 968 square centimeters. a. 13cm b. 14cm c. 15cm

d. 18cm

Solution

Let's solve these questions one by one.

Q1: Find the ratio of the perimeters of two squares given their area ratio is 49:169.

Given:

  • The ratio of the areas of two squares is 49:169.

Let the sides of the squares be a1a_1 and a2a_2. The ratio of the areas of the squares is given by: a12a22=49169\frac{a_1^2}{a_2^2} = \frac{49}{169}

Taking the square root of both sides to find the ratio of the sides: a1a2=49169=713\frac{a_1}{a_2} = \frac{\sqrt{49}}{\sqrt{169}} = \frac{7}{13}

The ratio of the perimeters of the squares, which is proportional to their sides, is also 7:13.

Answer: a. 7:13\text{a. 7:13}


Q2: Find the correct statement for the cuboid with dimensions 16m, 14m, and 7m.

Given:

  • Length l=16ml = 16 \, \text{m}
  • Breadth b=14mb = 14 \, \text{m}
  • Height h=7mh = 7 \, \text{m}
  1. Volume of the cuboid: Volume=l×b×h=16×14×7=1568cubic meters\text{Volume} = l \times b \times h = 16 \times 14 \times 7 = 1568 \, \text{cubic meters}

  2. Lateral Surface Area (LSA): LSA=2h(l+b)=2×7×(16+14)=2×7×30=420square meters\text{LSA} = 2h(l + b) = 2 \times 7 \times (16 + 14) = 2 \times 7 \times 30 = 420 \, \text{square meters}

  3. Ratio of Volume and LSA: VolumeLSA=1568420=392105\frac{\text{Volume}}{\text{LSA}} = \frac{1568}{420} = \frac{392}{105}

All of these calculations are correct.

Answer: d. All of the above\text{d. All of the above}


Q3: Find the length of the longest pole that can be placed in a room with dimensions 12m, 8m, and 9m.

The longest pole that can be placed in a room corresponds to the diagonal of the cuboid. The length of the diagonal dd of the cuboid is given by: d=l2+b2+h2=122+82+92=144+64+81=289=17md = \sqrt{l^2 + b^2 + h^2} = \sqrt{12^2 + 8^2 + 9^2} = \sqrt{144 + 64 + 81} = \sqrt{289} = 17 \, \text{m}

Answer: b. 17 m\text{b. 17 m}


Q4: Find the diameter of a sphere if the ratio of its volume to surface area is 27 cm.

Given:

  • Ratio of volume to surface area = 27 cm.

The volume VV and surface area AA of a sphere are given by: V=43πr3V = \frac{4}{3} \pi r^3 A=4πr2A = 4 \pi r^2 Given: VA=27\frac{V}{A} = 27

Substitute the formulas: 43πr34πr2=27\frac{\frac{4}{3} \pi r^3}{4 \pi r^2} = 27

Simplify: r3=27r=81cm\frac{r}{3} = 27 \quad \Rightarrow \quad r = 81 \, \text{cm}

The diameter DD of the sphere is: D=2r=2×81=162cmD = 2r = 2 \times 81 = 162 \, \text{cm}

Answer: c. 162 cm\text{c. 162 cm}


Q5: Find the height of a cylinder with radius 7 cm and total surface area of 968 square cm.

Given:

  • Radius r=7cmr = 7 \, \text{cm}
  • Total Surface Area A=968cm2A = 968 \, \text{cm}^2

The total surface area AA of a cylinder is given by: A=2πr(r+h)A = 2\pi r (r + h)

Substitute the given values: 968=2×22/7×7×(7+h)968 = 2 \times 22/7 \times 7 \times (7 + h)

Simplify: 968=44×(7+h)968 = 44 \times (7 + h)

Divide both sides by 44: 22=7+hh=15cm22 = 7 + h \quad \Rightarrow \quad h = 15 \, \text{cm}

Answer: c. 15 cm\text{c. 15 cm}


Do you want details or have any questions?

Related Questions:

  1. How do you find the area ratio of two squares from their side length ratio?
  2. What is the formula for the lateral surface area of a cuboid?
  3. How does the diagonal formula change if the cuboid's height is doubled?
  4. What would the ratio of volume to surface area be if the radius of the sphere was halved?
  5. How does the total surface area of a cylinder change with a different height?
  6. What is the volume of the cuboid if the breadth was reduced by 50%?
  7. What is the relation between radius and height for the cylinder's surface area?
  8. How does the volume of the sphere compare to its surface area?

Tip: For geometric problems, visualizing the shape and writing down all relevant formulas can help in solving problems more accurately.

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Math Problem Analysis

Mathematical Concepts

Geometry
Volume and Surface Area
Ratio and Proportion

Formulas

Volume of cuboid
Lateral Surface Area of cuboid
Volume of sphere
Surface area of sphere
Surface area of cylinder

Theorems

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Suitable Grade Level

Grades 7-9