Answer:
1.05 meters
Explanation:
Let the length of the rectangular backboard be x
Width = 1.8 m = 180 cm 
Area of rectangular backboard = 

Area of rectangular backboard = 

We are given that area is 18,900 sq.cm
So, 



So, length = 105 cm= 1.05 m 
Hence the backboard’s length in 1.05 meters