Meaning/Usage: Describes something that is easy to do.(描述某事非常容易)
Explanation: In the 1870's, cakes were given as prizes for winning competition. To the winner, it was an easy task. Therefore, "cake" started representing something easy. Another phrase that is similar is "cake walk," which also represents something that is easy.
"You won't have any problems with it. It's a piece of cake."
"It's not that difficult. Actually, it's a piece of cake."
"Learning to type is a piece of cake. It just takes persistence."
"Sociology 101 is a piece of cake. You should get an A in that class."
A: "I have an interview for citizenship tomorrow. Do you know what they ask?"
B: "The only questions they ask are in the manual they provide."
A: "Was it difficult?"
B: "Since all the questions and answers are already provided, it was a piece of cake."
Other Common Sentences
"My homework today was as easy as pie."
"The assignment was a breeze."