How many kgs of Basmati rice costing Rs 42 kg should a shopkeeper mix with 25 kgs of ordinary rice c...........

Explanation:

As the trader makes 25% profit by selling the mixture at Rs.40/kg, his cost per kg of the mixture = Rs.32/kg. 

C.P of  1 kg of rice of  1st kind = Rs. 42

C.P of  1 kg of rice of  2nd kind = Rs.

Mean price = Rs. 40 ( 25% profit , so cp will be  32 rs per kg )

By the rule of Alligation, we have:

C.P. of 1kg of                    C.P. of 1kg of

rice of 1st                          rice of 2nd

kind (Rs. 42)                      kind (Rs. 24)

                    \                    /

                     Mean Price
                         (Rs. 32)

                   /                    \

       32 - 24          :            42 - 32  

          (8)                              (10)

Let the amount of Basmati rice being mixed be x kgs

8 : 10 = x : 25

4/5 = x/25

x = 20 kgs.

Hence, option 4 is the correct answer.