1. A farmer has a bag of apples, and he wants to share it with his three sons. But he found that these apples were not divisible by 3, so he decided to give the remaining apples to his youngest son. Then he told his sons that they could share the apples equally, but they had to find the greatest common factor. Can you help his sons find this common ground?

There are two countries. Each country has some gold coins. One country has 70 gold coins, and another country has 90 gold coins. They decided to divide the gold coins equally among the soldiers. However, they can't cut the gold coin into pieces and need to find the greatest common denominator of their own gold coins. Can you help them find this common ground?

Three friends decided to buy a football together. First friend 50 yuan, second friend 40 yuan and third friend 30 yuan. They want to buy a football with their money, but they don't know how much to buy. Can you help them find a common ground so that their money can be used to buy football together?

There is a small town where every family grows some flowers. The first family planted 30 flowers, the second family planted 45 flowers and the third family planted 60 flowers. The mayor decided to distribute these flowers to all families equally, but he needed to find the greatest common denominator of the number of flowers planted by all families. Can you help the mayor find this common factor?

Two farmers decided to buy a cow together. The first farmer has 15 cows, and the second farmer has 20 cows. They want to buy a cow with their cows, but they don't know how much to buy. Can you help them find a common factor so that their cattle can be used together to buy cattle?