Answer :
6 blades in 1 windmill is the "unit rate" A unit rate is the number per thing. You will need to multiply. Multiply 6X7. 6 for 6 blades and 7 for 7 windmills. It is 42. 42 blades are in 7 windmills.
Well if you take 6x7 you get 42. If each windmill has 6 blades on it and there are 7 windmills you just take those two numbers and multiply them.
