Answer
given,
mass of the shell = 87 g = 0.087 Kg
speed of the muzzle = 853 m/s
mass of the helicopter = 4410 kg
A burst of 176 shell fired in 2.93 s
resulting average force = ?
momentum of the shell = m v
= 0.087 x 853
= 74.21 kgm/s
momentum of 176 shell is = 176 p
= 176 x 74.21
= 13060.96
momentum of helicopter = - 13060.96 kgm/s
amount of speed reduce a = 
a= 
a = 2.96 m/s²
velocity = \dfrac{2.96}{2.93}
v = 1.01 m/s
They are too small are never in the same place. Electrons are constantly moving in random motion within the electron cloud, making them impossible to follow.
The rule is always the same. Your final answer must have the same number of significant figures as the least accurate value in the calculation (one with the least number of significant figures) I hope this makes sense