51 men can complete a work in 12 days. Four days after they started working 6 more men joined them. How many days will they now take to complete the remaining work?

Correct option is C

Given:

51 men can complete a work in 12 days.

Four days after they started working 6 more men joined them.

Solution:  

Total work = 51 $$\times 12 = 612$$  unit

According to the question 

612 unit = $$51\times 4 + 57 \times D$$ 

57D = 408 

19D = 136

D = $$7\frac{3}{19}$$ days ​

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