2. A group of four friends were collecting plastic bottles. Nikola collected 72 bottles, Vlado collected a third less than Nikola, and Petar collected a third more than Vlado. Marko concluded that he, along with Vlado and Petar, collected twice as many bottles as Nikola. How many bottles did Marko collect?
First method:

Vlado collected $\frac{2}{3} \cdot 72=48$ bottles.

1 POINT

Petar collected $\frac{4}{3} \cdot 48=64$ bottles.

1 POINT

Marko, Vlado, and Petar together collected $72 \cdot 2=144$ bottles.

1 POINT

Since $144-(48+64)=144-112=32$,

2 POINTS

this means that Marko collected 32 plastic bottles.

1 POINT