A piece of cake

Also Can Be Phrased: 
piece of cake
Brief Definition: 
Easy to do or accomplish.
Further Explanation: 
Many believe that this idiom came into usage because dessert, especially cake, is usually the most anticipated part of a meal and therefore, easy to eat.
Examples: 
That calculus problem was surprisingly a piece of cake!
This time I knew what to do so it was a piece of cake.
Idiom Ratings
Popularity (Scale 1 to 5): 
3
Formality (Scale 1 to 5): 
3