Is 4 miles smaller bigger or equal to 15,840 feet

It is one mile longer than 15, 840 feet so bigger

4 miles * 5,280 feet in a mile equals to 21,120 feet. 21,120>15,840. Yes, four miles is greater than 15,840 feet.

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.