Question

sol. (3) Let the whole work be completed in ( x ) days
A's 1 day's work ( =frac{1}{10} )
B's 1 day's work ( =frac{1}{12} )
C's 1 day's work ( =frac{1}{15} )
According to the question, A's ( (x-5) ) days' work ( + ) B's ( (x-3) ) days' work ( + ) C's ( x ) days' work ( =1 )
( Rightarrow frac{x-5}{10}+frac{x-3}{12}+frac{x}{15}=1 )
( Rightarrow frac{6(x-5)+5(x-3)+4 x}{60}=1 )
( Rightarrow 6 x-30+5 x-15+4 x=60 )
( Rightarrow 15 x-45=60 Rightarrow 15 x=60+45=105 )
( Rightarrow x=frac{105}{15}=7 ) days

# Ex.6. A, B and C can complete a work in 10, 12 and 15 days respectively. A left the work 5 days before the work was completed and B left 2 days after A had left. Number of days required to complete the whole work is : (1) 8 (3) 7 (2) 6 (4) 6

Solution