At an elevation of 1221.4 feet, Lake Mead will hold 28,945,000 acre-feet of water. Which number is the BEST estimate of this amount of water?

3×10 6

2×10 7

3×10 7

2×10 8

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.