Which of the following usually have a positive correlation? select all that apply.
the amount of time studying and the grade on a science exam
the outside temperature and the amount of heating oil used
the weight of a car and the number of miles per gallon
the amount of time training and the total distance run

Find the greatest common factor of -30x 4 yz 3 and 75x 4 z 2.

Suppose that the price p (in dollars) and the weekly sales x (in thousands of units) of a certain commodity satisfy the demand equation 4p cubedplusx squaredequals38 comma 400. determine the rate at which sales are changing at a time when xequals80, pequals20, and the price is falling at the rate of $.20 per week.

If the speed of an electromagnetic wave is 100,000 cm/s and its wavelength is 100 cm, what is its frequency? a) 100,000 cycles per second (hz) b) 1 × 10-3 cycles per second (hz) c) 10,000,000 cycles per second (hz) d) 1,000 cycles per second (hz)