# Find the area to be painted in the following block with a cylindrical hole. Given that length is 15 cm, width 12 cm, height 20 cm and radius of the hole 2.8 cm.

**Solution:**

The area to be painted consists of:

1)The four side walls of the block,

2) The top face of the block

3) The Bottom face of the block

1)The area of the four side walls are:

2 × (15 × 20) + 2 × (12 × 20)

= 600 + 480

=1080cm²

2) The area of the top and bottom face

= 2 × (12 × 15) - 2 × (π × 2.8²)

= 360 - 2 × (22/7) × 2.8 × 2.8

= 360 - 49.28

= 310.72cm²

The area to be painted = 1080 + 310.72 = 1390.72cm²

**✦ Try This: **Find the area to be painted in the following block with a cylindrical hole. Given that length is 15 cm, width 12 cm, height 20 cm and radius of the hole 3.5 cm.

The area to be painted consists of:

1)The four side walls of the block,

2) The top face of the block

3) The Bottom face of the block

1)The area of the four side walls are:

2 × (20 × 25) + 2 × (12 × 25)

= 1000 + 300

=1300cm²

2) The area of the top and bottom face

= 2 × (12 × 20) - 2 × (π × 3.5²)

= 480 - 2 × (22/7) × 3.5 × 3.5

= 480 - 77

= 403cm²

The area to be painted = 1300 + 403 = 1703cm²

**☛ Also Check:** NCERT Solutions for Class 8 Maths Chapter 11

**NCERT Exemplar Class 8 Maths Chapter 11 Problem 100**

## Find the area to be painted in the following block with a cylindrical hole. Given that length is 15 cm, width 12 cm, height 20 cm and radius of the hole 2.8 cm.

**Summary:**

The area to be painted in the following block with a cylindrical hole, given that length is 15 cm, width 12 cm, height 20 cm and radius of the hole 2.8 cm, is 1390.72cm²

**☛ Related Questions:**

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