How do you round 673 grams to the nearest ten grams

"If the number you are rounding is followed by 5, 6, 7, 8, or 9, round the number up. Example: 38 rounded to the nearest ten is 40. ... If the number you are rounding is followed by 0, 1, 2, 3, or 4, round the number down. Example: 33 rounded to the nearest ten is 30."
-Fact Monster

Because 3 is lower then 5 we round 673 to 67.

The answer is "a"radius = 12.7 unitsdiameter = radius × 212.7 units × 2 = 25.4 units