From the formula given:
A = 150 ft², π ≈ 3.14
r = √(A/π)
r = √(150/π)
r = √(150/3.14) use calculator
r ≈ 6.911
r ≈ 6.9
The tenth digit is 9, and the digit after it is 1, and that is not up to 5, so the 9 is not rounded up to 10, it remains as 9.
Radius is ≈ 6.9 feet to nearest tenth
Hope this helps.