A work could be completed in 100 days by some workers. However, due to the absence of 10 workers, it was completed in 110 days. The original number of workers was ?

Let total number of worker in beginning is N
$$\eqalign{ & {\text{According to the question,}} \cr & \frac{{{\text{N}} \times {{100}_{{\text{days}}}}}}{{{1_{{\text{work}}}}}} = \frac{{\left( {{\text{N}} - 10} \right) \times {{110}_{{\text{days}}}}}}{{{1_{{\text{work}}}}}} \cr & 100{\text{N}} = {\text{110N}} - {\text{1100}} \cr & \Rightarrow {\text{10N}} = {\text{1100}} \cr & \Rightarrow {\text{N}} = {\text{110}} \cr} $$