The ratio of the efficiencies of A, B and C is 4 : 5 : 3 Working together, they can complete that work in 25 days. A and C together will complete 35% of that work in:

As per the given question,

The ratio in the efficiencies of A, B and C =4:5:3

Hence, A can complete the work in x/4 days

B can complete the work in x/5 days

C can finish the work in x/3 days

So, the work will be finish in one day, if they are working together $$\dfrac{4}{x}+\dfrac{5}{x}+\dfrac{3}{x}=\dfrac{1}{25}$$

$$\Rightarrow \dfrac{4+5+3}{x}=\dfrac{1}{25}$$

$$\Rightarrow \dfrac{12}{x}=\dfrac{1}{25}$$

$$\Rightarrow x=300$$

Hence, A alone can finish the work $$=\dfrac{300}{4}=75$$days

C alone can finish the wok $$=\dfrac{300}{3}=100$$days

A and C can finish the work together in one day $$=\dfrac{1}{75}+\dfrac{1}{100}=\dfrac{4+3}{300}=\dfrac{7}{300}$$

Hence, A and C can finish the work in $$=\dfrac{300}{7}$$ days

Hence, A and C can finish 35% work $$=\dfrac{300\times 35}{7\times 100}=15$$ days