Question

worksheet 21
date: .................
find the perimeter of the following rectangle - shaped figures.
1)
0.5 m
2 m
perimeter = 2(l + b) = 2(2 + 0.5) m
= 2 × 2.5 m = 5 m
2)
52 cm
28 cm
3)
6.5 cm
19 cm
chocolate
bar
4)
7 cm
3 cm
5)
2 m
1.5 m
a + b =
6)
27 cm
45 cm
time: minutes
teachers signature: .......................
21

Explanation:

planation:

Step1: Use the formula for the perimeter of a rectangle

The formula for the perimeter of a rectangle is \(P = 2(l + b)\), where \(l\) is the length and \(b\) is the breadth.

Step2: Calculate for each figure

2)

For the suitcase with \(l = 52\) cm and \(b=28\) cm:
\(P = 2(52 + 28)\)
\(=2\times80\)
\( = 160\) cm

3)

For the chocolate - bar - shaped figure with \(l = 19\) cm and \(b = 6.5\) cm:
\(P=2(19 + 6.5)\)
\(=2\times25.5\)
\(=51\) cm

4)

For the domino - shaped figure with \(l = 7\) cm and \(b = 3\) cm:
\(P=2(7 + 3)\)
\(=2\times10\)
\(=20\) cm

5)

For the black - board - shaped figure with \(l = 2\) m and \(b = 1.5\) m:
\(P=2(2 + 1.5)\)
\(=2\times3.5\)
\(=7\) m

6)

For the notebook - shaped figure with \(l = 45\) cm and \(b = 27\) cm:
\(P=2(45 + 27)\)
\(=2\times72\)
\(=144\) cm

Answer:

1. \(160\) cm
2. \(51\) cm
3. \(20\) cm
4. \(7\) m
5. \(144\) cm