Both Euler and Mark were born in the city, and they decided to follow their uncle who planted grapes to the farmhouse. They went into their uncle's garden and saw his two sons picking cucumbers in the garden. Mark saw a basket full of cucumbers and asked, "How many cucumbers did you pick?" The naughty little son didn't answer, but clapped his hands and sang children's songs: "Two brothers picked cucumbers, one picked seven or eight, and the other picked eight. How many melons did they each pick? " Euler smiled: "Haha, the children are testing us." He thought for a moment and said, "My brother picked thirty-five and my brother picked forty-three."

Euler and Mark and their uncle came to the back garden. When they saw aunt calling ducks to cages by the river, Euler asked enthusiastically, "How many ducks does aunt keep?"? Let us help you catch them. " Aunt also happily sang: "The sun is setting and the sunset glow is red. I drove the ducks back to the pond. Half stay in the water screaming, half into the cage. The remaining fifteen are with me. How many ducks do I have? " Afraid that Euler would get ahead of him, Mark quickly said, "I know, 15×2×2=60."

In the evening, Euler, Mark and his uncle sat around the grape trellis. Uncle brought a big watermelon, smiled and handed Euler a melon cutter, saying, "If it's unusual, here's a melon cutting problem. Cut three knives into seven melons and eat the remaining eight skins. " Euler said awkwardly, "It's not difficult to cut into seven pieces, but how can you eat eight pieces of skin?" Mark suggested drawing a triangle on the stage, and Euler patted his forehead and said, "I see!" " "Not to be outdone after cutting the melon, Euler said," it's so strange. It is difficult to cut watermelon with a knife. Watermelon is big and round. Cut four knives into nine pieces, and there are ten skins left after eating! "

Euler and Mark spent another happy day, lying in bed, and they sincerely lamented: "There is mathematics everywhere in life!" " "