The total numbers of chocolates belonging to three of them

contest-mathelementary-number-theorynumber theorypuzzle

Pial gives half of his 20 chocolates to Zunayed so that Zunayed has more chocolates, Zunayed gives half of his chocolates to Bindu so that Bindu has more chocolates than
Zunayed. What is the total numbers of chocolates belonging to three of them?

Source: Bangladesh Math Olympiad 2018 junior category.

I can not understand the question properly. "Zunayed has more chocolates"- does it mean he has more chocolate than both Pial and Bindu or only Pial. Is there any valid solution of this question?

Best Answer

Assuming Zunayed has more chocolates than Pial and at the end it is not required to have $P<Z<B$, but only the intermediate steps. (Pial is not to blame if Zunayed decided to give away chocolates to Bindu).

Pial gives half of his 20 chocolates to Zunayed so that Zunayed has more chocolates (than Pial).

Can Zunayed have 3 chocolates? No, because Pial can give 9 chocolates so that $Z=12>11=P$. (According to the condition, Pial must give 10 and keep $\color{red}{10}$).

Can Zunayed have 2 chocolates? Yes, Zunayed has $\color{red}{2}$ chocolates.

Can Zunayed have 1 chocolate? No, because Zunayed gets 10 from Pial to have 11 in total, however, Zunayed can not give half of it to Bindu (it is assumed a chocolate is indivisible).

Zunayed gives half of his chocolates to Bindu so that Bindu has more chocolates than Zunayed.

First note that Zunayed has 12 chocolates after receiving 10 from Pial.

Can Bindu have 3 chocolates? No, because Zunayed has 12 chocolates and Zunayed can give 5 to Bindu, because $B=8>7=Z$. (According to the condition, Zunayed must give 6).

Can Bindu have 2 or 1 chocolates? Yes, Bindu has $\color{red}{2}$ or $\color{red}{1}$ chocolates.

Hence, the total number of chocolates is $\color{red}{24}$ or $\color{red}{23}$. That is: $$P=20,Z=2,B=2 \ \ \text{or} \ \ P=20,Z=2,B=1$$ in the beginning.