A pebble is dropped into a deep well and 3s later the sound of a splash is heard as the pebble reaches the bottom of the well. The speed of sound in air is about 340 m/s. How long will it take fir the pebble to hit the water? How long does is take for the sound to reach the observer? What is the depth of the well? (I need the equation)

The circumference of a circle is 5 pi cm. what is the area of the circle?

1- 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. 2- what do you think the product of a nonzero rational number and an irrational number is? is it rational or irrational? make use of variables, the closure property of integers, and possibly a proof by contradiction to prove your hypothesis. 3- why do we have to specify that the rational number must be nonzero when we determine what the product of a nonzero rational number and an irrational number is? if the rational number were 0, would it give us the same result we found in part b?

Asequence is defined recursively using the formula f(n + 1) =f(n) - 5. which sequence could be