3/7 multiplied by 21 = 3/7 x 21 = 9 = 3/7 x 21/1 = 63/7 = 9
Or if you can't do the math - Think of a pizza with 21 slices . Now cut this pizza into 7 equal parts. You will find that each part contains exactly 3 slices. Now, eat 3 of these parts. With three slices in each part, you ate 9 slices - which is three sevenths of 21.
