Which choices are equivalent to the expression? √(5) x √(20)

What is the simplified form of (3.25x10^3)(7.8x10^6) written in scientific notation?

If i have 20$ and i gave 5$ away how much i got

Is the product of two rational numbers irrational or rational? first, make a hypothesis by multiplying two rational numbers. then, use variables such as x=a/b and y=c/d and the closure property of integers to prove your hypothesis.