554 Chapter 6 Percent
2 Estimate answers to percent problems
involving 50%, 25%, 5%, and 15%.
There is an easy way to find 50% of a number. First, recall that 50% 10050 ^12. Thus,
to find 50% of a number means to find of that number, and to find of a number we
simply divide it by 2.12 12Finding 50% of a NumberTo find 50% of a number, divide the number by 2.EXAMPLE (^4) Estimate the answer: What is 50% of 2,595,603?
StrategyWe will divide an approximation of 2,595,603 by 2.
WHYTo find 50% of a number, we divide the number by 2.
SolutionTo estimate 50% of 2,595,603, we will find 50% of 2,600,000. We use
2,600,000 as an approximation because it is close to 2,595,603, because it is even,
and, therefore, divisible by 2, and because it ends with many zeros.
50% of 2,595,6031,300,000 Because 50% of 2,600,0002,600,000 2 1,300,000
Self Check 4
Estimate the answer: What is
50% of 14,272,549?
Now TryProblem 23
There is also an easy way to find 25% of a number. First, find 50% of the number
by dividing the number by 2. Then, since 25% is one-half of 50%, divide that result by
- Or, to save time, simply divide the original number by 4.
Finding 25% of a NumberTo find 25% of a number, divide the number by 4.EXAMPLE (^5) Estimate the answer: What is 25% of 43.02?
StrategyWe will divide an approximation of 43.02 by 4.
WHYTo find 25% of a number, divide the number by 4.
SolutionTo estimate 25% of 43.02, we will find 25% of 44. We use 44 as an
approximation because it is close to 43.02 and because it is divisible by 4.
25% of 43.02 11 Because 25% of 44 ^444 11.
Self Check 5
Estimate the answer: What is
25% of 27.16?
Now TryProblem 27
There is a quick way to find 5% of a number. First, find 10% of the number by
moving the decimal point in the number one place to the left. Then, since 5% is one-
half of 10%, divide that result by 2.
Finding 5% of a Number
To find 5% of a number, find 10% of the number by moving the decimal point
in the number one place to the left. Then, divide that result by 2.