Business Mathematics Brief 12th Edition by Stanley Salzman ,Gary Clendenen, Charles Miller

Exercise 5

Estimate answer using front-end rounding. Then find the exact answer. (See Example.)

Using Front-end Rounding to Estimate an Answer
The graphic shows the top oil producing areas in the U.S. Notice that a lot of oil is produced offshore in the Gulf of Mexico. Apply front-end rounding to estimate total oil production from these areas.

Quick TIP
In front-end rounding, only one nonzero digit (first digit) remains. All digits to the right are zeros.
Solution
Oil consumption in the U.S. is about 7,000,000,000 barrels. The U.S. must buy the difference between what is consumed and what is produced in the U.S. It buys oil from Canada, Saudi Arabia and other oil exporting nations.