Question

in how many ways can i write letters to three out of 9 friends if i have exactly one post card,one inland letter and one envelope?​

Answer 1

Answer:

504

Step-by-step explanation:

Selecting 3 out of 9 friends, thus--->

9c3 = 9! / (9-3)! x 3!

       

But arranging also matters, thus multiply by 3!

9! / (9-3)! x 3!      x 3!

= 9! / 6!                                               [Cancelling out 3!]

= 9 x 8 x 7

= 504 ways!

Hope you understand!