What scale measures the strength of tornadoes

The EF Scale is the standard way to measure tornadoes based on wind damage. The original Fujita Scale (or F Scale) was developed by Dr. Theodore Fujita. 

The EF Scale (below) is the standard way to measure tornadoes based on wind damage. The original Fujita Scale (or F Scale) was developed by Dr. Theodore Fujita. All tornadoes, and other severe local windstorms, were assigned a number according to the most intense damage caused by the storm

This is what i did 45-5=4040÷4=10so there are 10 white marbles but am not sure is just a question that am not sure