4.NF.4b: Understand a multiple of a/b as a multiple of 1/b, and use this understanding to multiply a fraction by a whole number. For example, use a visual fraction model to express 3 ⋅ 2/5 as 6 ⋅ 1/5, recognizing this product as 6/5. (In general, n ⋅ a/b = n⋅a/b.).