Given that 16 workers take 48 hours to build the wall. If the time is reduced to 32 hours, then let the number of workers required be y.
16 × 48 = y × 32
y = 24 (1 mark)
Now, since 4 workers got injured and left after accident, the remaining number of workers at the site is 16-4 = 12
Thus, additional number of workers required will be 24 - 12 = 12. (1 mark)