Question

Story on the topic taking a walk with friendly microbes you can take the reference of chapter microorganism and foe

Answer 1

Explanation:

Question 2.

Calculate the edge of the cube if its volume is 1331 cm3.

Solution:

Volume of cube = 1331 cm3

(Side)3 = 1331

Side = (11 × 11 × 11)13 = 11 cm

Question 3.

The curved surface area of a cone is 12320 sq. cm, if the radius of its base is 56 cm, find its

height.

Solution:

Here, radius of base of a cone (r) = 56 cm

And, curved surface area = 12320 cm2

πrl = 12320

l = 12320πr

= 12320×722×56 = 70 cm

Again, we have

r2 + h2 = l2

h2 = l2 – r2 = 702 – 562

= 4900 – 3136 = 1764

h = √1764 = 42 cm

Hence, the height of the cone is 42 cm.

Question 4.

Two cubes of edge 6 cm are joined to form a cuboid. Find the total surface area of the cuboid.

Solution:

When two cubes are joined end to end, then

Length of the cuboid = 6 + 6 = 12 cm

Breadth of the cuboid = 6 cm

Height of the cuboid = 6 cm

Total surface area of the cuboid = 2 (lb + bh + hl)

= 2(12 × 6 + 6 × 6 + 6 × 12)

= 2(72 + 36 + 72) = 2(180)

= 360 cm2

Question 5.

A metallic sphere is of radius 4.9 cm. If the density of the metal is 7.8 g/cm2, find the mass of the sphere (π = 227).

Solution:

Here, radius of metallic sphere (r) = 4.9 cm

The volume of a solid hemisphere is 1152 π cm3. Find its curved surface area.

Solution:

Here, volume of hemisphere = 1152 π cm3

∴ 23πr3 = 1152

⇒ r3 = (12)3 π

⇒ r1152×32 = 1728

⇒ r3 = (12)3

Now, curved surface area = 2πr2

= 2 × π × (12)2 = 288π cm2