Final answer:
The new mean height of the group is 148.105 cm.
Step-by-step explanation:
To find the new mean height, we need to subtract the height of the pupil who left the group from the previous mean height, and then divide by the number of remaining pupils.
The calculation is as follows:
New mean height = (Sum of previous heights - height of pupil who left) / (Number of remaining pupils)
New mean height = (149 * 20 - 176) / 19
New mean height = 148.105 cm
Therefore, the new mean height of the group is 148.105 cm.