7.2 Vasya saved 80 rubles in 5-kopeck coins. To pay off a debt of 25 rubles to his friend, he started counting the coins, but got confused and decided to use a balance scale. How can he separate the required amount in 4 weighings, if he has no weights?
7.2 Vasya has saved 80 rubles in 5-kopeck coins. To pay off a debt of 25 rubles to his friend, he started counting the coins but got confused and decided to use a balance scale. How can he separate the required amount in 4 weighings, if he has no weights?

Hint: In the first weighing, Vasya divides all the coins into two equal-weight piles and gets two piles of 40 rubles each. Then he similarly divides one of the 40-ruble piles into two equal parts. By repeating this process two more times, he will end up with two piles of 5 rubles and three piles of 10, 20, and 40 rubles. By combining the 5-ruble and 20-ruble piles, he will get the required amount.