英文數學題2問.急!!!!20分

The length of a basketball court is measured to be 29m,correct to the nearest 0.5m.
The diameter of a basketball is measured to be 24cm,correct　to the nearest cm.
我想請問一下怎樣correct to the nearest 0.5m
怎樣correct to the nearest cm
Actually, in these questions , the answer can be easily seen.
For the basketball court, if it correst to the nearest 0.5m
It's length = 29.0m ( correst to the nearest 0.5m)
For the basketball. if it is correct to the nearest cm
It's diameter = 24 cm ( correst to the nearest 1 cm )
For both of them, the number hasn't changed since they both don't have the decimal places which is after the correcting place
The time that John takes to finish a 100m race is measured to be 12.6s
,correct to the nearest 0.2s.
我想請問一下怎樣correct to the nearest 0.2s
For the time to finish a 100m race
The time needed = 12.6s ( correct to the nearest 0.2s)
Since 0.6 is also one of the multiple of 0.2, so the number won't change