S.P. of 1 kg of the mixture = Rs. 68.20, Gain = 10%.

C.P. of 1 kg of the mixture = Rs.{100/110}x 68.20= Rs. 62   

Explanation :

 A's 1 hour's work =1/4

 ; (B + C)'s 1 hour's work =1/3

 ; (A + C)'s 1 hour's work =1/2

 (A + B + C)'s 1 hour's work =1/4+1/3

 =7/12

 (A + B + C)'s 1 hour's work =1/4+1/3=7/12

 B's 1 hour's work =7/12-1/2 =1/12

  B alone will take 12 hours to do the work.

Explanation :

 Part of the work done by A ={1/10}x 5=    1/2

 Part of the work done by B ={1/15}x 5=1/3

 Part of the work done by C = 1 -    1/2+1/3=1/6

 So, (A’s share) : (B’s share) : (C’s share) =1/2:1/3:1/6 = 3 : 2 : 1     

 A's share = Rs{.3/6}x 1500= Rs. 750, B's share = Rs.{2/6}x 1500 = Rs. 500.     

 C's share = Rs.{1/6}x 1500 = Rs. 250.         

 A’s daily wages = Rs.750/5

  = Rs. 150, B's daily wages = Rs.    500/5 = Rs. 100.     

 C’s daily wages = Rs.250/2

  = Rs. 125.         

 Daily wages of B and C = Rs. (100 + 125) = Rs. 225.

The time the distance between A & B will be 24m at two times when A has covered relative distance of 36m or 84m. 

84/(17-13) = 21s

Let, speed of train = x km/hr 

Relative speed while crossing 1st person = 5 ( x − 3) 18

Distance = length of train = 5 ( x − 3)× 9 ··· (I) 18

Relative speed while crossing 2nd person

= 5 ( x − 6) 18

x = 33 km/hr