Answer:
0.42 and 0.55
Explanation:
First work out the mean length of the batch:-
= (0.42 + 0.53 + 0.55 + 0.48 + 0.51) / 5
= 0.498
Check each nail against this mean:-
0.42 is 0.078 less than the mean so should be thrown out
the other one is 0.55 ( as 0.55 - 0.498 = 0.52 more than the mean))