1 of 5

SURFACE AREAS

AND VOLUMES

Sum based on Cylinder and Cuboid

2 of 5

1.75 cm

2 mm

10cm

5.5 cm

3.5 cm

=

N =

Vol. of cuboid

Vol. of 1 silver coin

Vol. of N silver coins =

Vol. of Cuboid

Sol.

N × Vol. of 1 silver coin

=

Vol. of Cuboid

Radius (r)

=

1.75

2

cm

Q. How many silver coins, 1.75 cm in diameter and of

thickness 2mm, must be melted to form a cuboid of

dimensions 5.5 cm × 10 cm × 3.5 cm?

Silver coins are melted

to form a cuboid

3 of 5

Q. How many silver coins, 1.75 cm in diameter and of

thickness 2mm, must be melted to form a cuboid of

dimensions 5.5 cm × 10 cm × 3.5 cm?

Vol. of 1 silver coin

=

πr²h₂

Sol.

∴

=

×

2

10

1.75

2

Vol. of cuboid

=

l

×

b

×

h₁

=

5.5

×

10

×

3.5

cm³

What is the formula for

volume of cuboid ?

l × b × h

22

7

×

1.75

2

∴ Vol. of cuboid

What is the formula for

volume of cylinder?

πr²h

Vol. of 1 silver coin

55

10

×

35

10

× 10

=

What is the shape of silver coins?

Cylinder

N =

Vol. of cuboid

Vol. of 1 silver coin

Radius (r)

=

1.75

2

cm

4 of 5

Q. How many silver coins, 1.75 cm in diameter and of

thickness 2mm, must be melted to form a cuboid of

dimensions 5.5 cm × 10 cm × 3.5 cm?

Sol.

=

×

2

10

1.75

2

22

7

×

1.75

2

Vol. of 1 silver coin

22

7

×

175

200

×

175

200

×

2

10

=

∴ Vol. of 1 silver coin

N

=

Vol. of cuboid (V₁)

Vol. of 1 silver coin (V₂)

∴

N

=

55

10

×

35

10

× 10

22

7

×

175

200

×

175

200

×

2

10

N =

Vol. of cuboid

Vol. of 1 silver coin

cm³

Vol. of cuboid

55

10

×

35

10

× 10

=

5 of 5

Q. How many silver coins, 1.75 cm in diameter and of

thickness 2mm, must be melted to form a cuboid of

dimensions 5.5 cm × 10 cm × 3.5 cm?

Sol.

N

=

55

10

×

35

10

× 10

22

7

×

175

200

×

175

200

×

2

10

=

55

10

×

35

10

× 10

7

22

×

200

175

×

200

175

×

10

2

×

11

40

35

20

40

35

8

5

4

5

=

∴ 400 coins must be melted.

×

5

×

20

4

=

400

N =

Vol. of cuboid

Vol. of 1 silver coin