What are some good websites i can use to test my knowledge?

Formula that contains a nested function that first calculates the average of the values in range e6: p6 and uses the round function to round that average to the nearest 10 dollars. use -1 for the value of the number digit argument. would the formula be =round(average(e6: p6),0

What are "open-loop" and "closed-loop" systems

Two students are discussing the flow of electricity. student a says that voltage is a measure of the amount of electron flow in a circuit. student b says that power is the product of voltage and current. which of the following statements is correct? a. only student a is correct b. only student b is correct c. both of the two students are correct d. neither of the two students is correct