instruction:
Combine the given two facts to write a concluding fact. Note that there should be some parts of the first and second facts that are not mentioned in this conclusion fact. Your combined fact should be the result of a chain between the two facts. Chains form when two facts connect together to produce a concluding fact. An example of a chain is: "pesticides cause pollution" (fact1) + "pollution can harm animals" (fact2) → "pesticides can harm animals" (conclusion fact). Parts of the concluding fact overlap with the first and the second fact. To construct such a  concluding fact, a useful way is to borrow the subject from one fact and the ending conclusions from another fact.
question:
Fact 1: a speedometer is used for giving a driver feedback on the speed of their vehicle. 
Fact 2: Speed is the magnitude of velocity.
answer:
A speedometer is used for giving feedback on the velocity of a vehicle.


question:
Fact 1: Ethanol is produced by alcoholic fermentation of the glucose in corn or other plants. 
Fact 2: Ethanol is a fuel made of corn.
answer:
fermentation can be used to make fuel.


question:
Fact 1: when a metal rusts , that metal becomes orange on the surface. 
Fact 2: Yin metal is small metal, jewelery metal and decorative metal.
answer:

When jewelry rusts it may become orange on the surface.