Clinical signs are usually seen 3-5 days after exposure. Second-generation coumarins and indandiones are toxic with a single dose. Second-generation coumarins are a greater hazard than first-generation coumarins if the dog or cat eats a poisoned rat or mouse.
Quick Answer. Fractions were created by the ancient Egyptians in 1800 B.C. Egyptians created a number system on a base 10 concept, which is similar to the numerical systems used in the United States and around the world for creating fractions. Originally, Egyptians used pictures as well as numerals to display and differentiate numbers.
This gives rise to a new and different kind of number -- a fraction. It is a number we need for measuring rather than counting. We are then able to say that a certain length, for example, is 5Â¼ cm. And so what we call a proper fraction is a number less than 1. Fractions belong to what is continuous rather than what is discrete. See The Evolution of the Real Numbers, Lesson 3. We will see that everything we have learned about ratios will apply to fractions, because, as we will see, each numerator has a ratio to its denominator.