Ravi makes lemonade by mixing lemon juice and water. For every 1 cup of lemon juice, he uses 4 cups of water. What is the correct number of each ingredient to make 10 cups of lemonade?
For every 1 cup of lemon juice, Ravi uses 4 cups of water, so for 10 cups of lemonade, he would use 10/4 = <<10/4=2.5>>2.5 cups of lemon juice.
Since he cannot use half a cup, he would use 2 cups of lemon juice.
He would use a total of 2 cups of lemon juice and 2*4 = <<2*4=8>>8 cups of water. Answer: \boxed{2,8}.