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The volume of construction work was increased by 60%, but the productivity of labor increased by only 25%.
By what percent must the workers be increased?
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Let V be the original volume of construction work (the volume "before"),
r be the productivity of labor "before",
N be the number of workers "before", and
x be in what percent the number of workers must be increased.
According to the condition, these quantities are constrained/connected by the equations
V = r*N, (1) and
1.6*V = 1.25r*N*(1+x). (2)
From these equations,
x = = = = 1.28 - 1 = 0.28.
Answer. The number of workers must be increased by 28%.