Three friends, camping and logs of wood!

I wasn’t keeping well – nothing too serious though – over the past few days, and going through a slight bout of depression doesn’t help very much either. I think I have recovered now. During such periods, it helps (I think) to keep the mind busy over some light puzzle(s) just so it remains active and healthy. Anyway, let me pose a nice puzzle that I first read in a book by Yakov I. Perelman many years ago, and I invite you to post your solutions. In keeping with the spirit of the puzzle, I will stick to Russian names and currency, even though the names I use below aren’t the same as the ones used in the original puzzle.

Anna, Bogdana and Calina are three young mathematicians who decide, one fine day, to go camping. During camping, in the evening they light a campfire to keep themselves warm and also to discuss (what else?) mathematics! Anna and Bogdana had brought with them three and five logs of wood, respectively, but unfortunately, Calina forgot to bring any log of wood with her. Instead, she gave 8 rubles to the other two girls. If Calina didn’t want any money back and if all the eight logs of wood were used for building the campfire, how should Anna and Bogdana distribute the 8 rubles between themselves in a fair manner?

Yakov Isidorovich Perelman

There is immense joy and thrill in discovering that one of the world’s greatest mathematicians (and probably many more like him) got interested in mathematics, just as I did as a kid, after reading one of Yakov I. Perelman‘s popular science books. Physics for Entertainment is the book and Grisha Perelman is the mathematician I am referring to!

Yakov I. Perelman’s books on physics, mathematics and astronomy were written in a style that brought out many of the aspects of the aforesaid subjects in the most enjoyable way. He breathed life into every page of his books and made mathematics and physics accessible to any kid in a way that brought sheer joy to the soul! At the same time, his writings provided a glimpse of the amazing way that physics helps us understand and study the nature around us. Physics Can Be Fun, Mathematics Can be Fun and Astronomy for Entertainment are the titles of some of his other books that were immensely popular among young students who read them. The credit for my long-lasting interest/passion in physics and mathematics solely goes to him.

I think all twelve-year olds should be given copies of his books as birthday gifts instead of toys! Surprisingly, there is an online copy of Physics For Entertainment here. I am not sure if any copyright laws will be violated if you download the online version but it seems that the site is a “genuine” one.

Yakov Perelman, sadly, died during the Siege of Leningrad in 1942.