Find the perimeter of a square with sides 10cm, 5cm, 6cm, 8cm.

Given:
a1 = 10 cm,
a2 = 5 cm,
a3 = 6 cm,
a4 = 8 cm.
P1 -?
P2 -?
P3 -?
P4 -?
Decision.
By definition of the perimeter of a square (the perimeter is the sum of all sides):
P = a + a + a + a = 4a. (1)
P1 = 4a1. (2)
P2 = 4a2. (3)
P3 = 4a3. (4)
P4 = 4a4. (5)
Substitute the numerical values in (2), (3), (4), (5):
P1 = 4 * 10 = 40 (cm) = 4 dm.
P2 = 4 * 5 = 20 (cm) = 2 dm.
P3 = 4 * 6 = 24 (cm) = 2.4 dm.
P4 = 4 * 8 = 32 (cm) = 3.2 dm.
Answer: P1 = 40 cm = 4 dm; P2 = 20 cm = 2 dm; P3 = 24 cm = 2.4 dm; P4 = 32 cm = 3.2 dm.