What number is the opposite of 0

Round to the nearest ten thousandth. i dont get this

Jocelyn estimates that a piece of wood measures 5.5 cm. if it actually measures 5.62 cm, what is the percent error of jocelyn’s estimate? a. 2.13% b. 2.18% c. 12% d. 46.83%

Robert plans to make a box-and-whisker plot of the following set of data. 27, 14, 46, 38, 32, 18, 21 find the lower quartile, the median, and the upper quartile of the set? lower quartile: 19.5; median: 29.5; upper quartile: 42 lower quartile: 14; median: 27; upper quartile: 46 lower quartile: 18; median: 27; upper quartile: 38 lower quartile: 16; median: 29.5; upper quartile: 42