Please help! I am really stressed out. there is more than 1 right answer!

Identify the missing numbers below to show the result of multiplying the numbers (1.6 × 10-19)(5.0 × 106) = c × 10d

The famous scientist galileo galilei did several experiments with sloping planes, which he rolled metal balls down so that he could study motion. by changing the slope, he could study how the speed at which the ball rolled was affected. what was the independent variable in galileo's experiment? a. the speed of the ball b. the slope of the plane c. whether the ball moved d. what the ball was made of

If 22.5 of nitrogen at 748 mm hg are compressed to 725 mm hg at constant temperature. what is the new volume?