How do you find 3/7 of 56? The idea is, we first find 1/7 of 56, which is the DIVISION problem 56 ÷ 7 = 8. Then, 3/7 of the quantity is three times that (three groups out of the seven), or 24.
First I show you this concept (finding a fractional part of a quantity) using pictures ,and then we work through some problems without pictures. This lesson is suitable for 4th grade math and onward.
Division with remainders — video lesson
Math Mammoth Division 2 — a workbook with worksheets and lessons for long division, remainder, factors, and primes
Math Mammoth Grade 4 curriculum