I am going to teach you how to estimate the square root of 19. First, you have to find the two  perfect square roots, for 19 the two perfect square roots are 16  which would be 4 and 25 would be 5. Second, you have to see how much that is which 16 and 25 equals to 4.5. Third, you have you have to add 4.5 to 16 so you can eliminate possibilities. 16+4.5=20.5 and 19 is a little less than 20.5. So, you can eliminate 4.5, 4.6, 4.7, 4.8, and 4.9.I would say the square root of 19 is 4.4.