the length of the diagonal can be determined using Pythagoras theorem
The Pythagoras theorem : a² + b² = c²
where a = length
b = base
c = hypotenuse
280² + 150²
= 78,400 + 22,500
= 100,900
take the square root of 100,900
= 317.648 feet
the tenth is the first number after the decimal place. To convert to the nearest tenth, look at the number after the tenth (the hundredth). If the number is greater or equal to 5, add 1 to the tenth figure. If this is not the case, add zero
The reason that it would be 0.364 is because the thousandths place is the third decimal place, which would leave you with a 3 but since there is a 6 after the 3, the 3 would be rounded up to a 4.