How many different flags with 3 stripes are possible using the colours red blue and yellow. each colour may be used more than once in each flag?

To determine the number of different flags with 3 stripes using the colors red, blue, and yellow, we can use the rule of multiplication. Each stripe can be one of the three colors, so for each of the 3 stripes, there are 3 choices. Thus, the total number of different flags is (3 \times 3 \times 3 = 3^3 = 27). Therefore, 27 different flags with 3 stripes can be created using the colors red, blue, and yellow.