Benchmark fractions are common and familiar fractions used for comparison of less familiar fractions. Benchmark fractions also help when estimating answers to addition or subtraction problems to determine whether an answer makes sense.
Benchmark fractions are easy for kids to visualize and understand, such as 1/4 or 1/2. They are often the first fractions students learn and become familiar with. If the student needs to compare 1/3 and 3/5, the benchmark of 1/2 helps determine which fraction is larger. If the student is familar with and understands that 1/3 is smaller than 1/2, while 3/5 is larger, therefore 3/5 is larger than 1/3.