The least number which approximates to 0.4mm to the nearest tenth is 0.35 while the largest number which approximates to 0.4mm to the nearest tenth is 0.449
Therefore, the minimum & maximum possible measurements are 0.35 and 0.449 respectively.
0.35mm-0.45mm
The actual length of the onion cell must be something that rounds to .4mm. Anything lower than 0.35mm would be closer to .3mm and anything over .45 would be closer to .5mm.
