4. the density and strength of concrete are determined by the ratio of cement and aggregate. suppose that a contractor has 480 cubic feet of a dry concrete mixture that is 70% sand by volume. how much pure sand must be added to form a new mixture that is 75% sand by volume?

Explain the difference between each pair of concepts. a. frequency and relative frequency b. percentage and relative frequency a. select the correct choice below. a. frequency is the total number of observations in a data set. relative frequency is the number of times a particular distinct value occurs. b. frequency is the number of times a particular distinct value occurs. relative frequency is the ratio of the frequency of a value to the total number of observations. c. frequency is the total number of observations in a data set. relative frequency is the ratio of the number of times a particular distinct value occurs to the frequency. d. frequency is the number of times a particular distinct value occurs. relative frequency is the ratio of the frequency of two different values.

Awave is produced in a rope. the wave has a speed of 33 m/s and a frequency of 22 hz.

An ideal gas is held in a container at constant volume. initially, its temperature is 5 degrees c and its pressure is 1.2 atm. what is its pressure when its temperature is 43 degrees c? answer in units of atm