External side including path = side of lawn + width of path on both sides.
= y + (2 + 2)
= y + 4
Total area including path = (y + 4) × (y + 4).
= y² + 8y + 16 (i).
And the area of lawn = (side)² = y × y = y² (ii).
Since the area of the path is given (160 m2), we have:
Area of path = Total area including path - area of lawn.
A = (i) - (ii).
Substitute the given values we will the following equation and by isolating y, we can determine the length of side of the lawn:
160 = (y² + 8y + 16) - y²
160 = y² + 8y + 16 - y²
160 = y² - y² + 8y + 16
160 = 8y + 16
160 - 16 = 8y
144 = 8y
18 = y
Side of lawn = 18 m
Area of the lawn = side × side
A = s²
A = 18 × 18
A = 324 m2
Hence the area of lawn = 324 m2.