Question

6400 workers were employed to construct a river bridge in four years. At the end of the first year, 25% workers were retrenched. At the end of the second year, 25% of those working at that time were retrenched. However, to complete the project in time, the number of workers was increased by 25% at the end of the third year. How many workers were working during the fourth year?

Answer 1

Number of workers = 6, 400
At the end of the first year, 25 % of the workers were retrenched.
∴ 25 % of 6, 400 = 1, 600
Number of workers at the end of the first year = 6, 400 - 1, 600 = 4, 800
At the end of the second year, 25 % of those working were retrenched.
∴ 25 % of 4, 800 = 1, 200
Number of workers at the end of the second year = 4, 800 - 1, 200 = 3, 600
At the end of the third year, 25 % of those working increased.
∴ 25 % of 3, 600 = 900
Number of workers at the end of the third year = 3, 600 + 900 = 4, 500
Thus, the number of workers during the fourth year was 4, 500.