A Guide to the GRE/Decimals
Decimals are an extension of the base ten numeral system to fractions of ten (such as hundredths and thousandths). In this way they are a variation of fractions and percentages.
Decimals are fractions of 10, 100, 1000, and so on.
You will have access to a calculator on the GRE but it is nonetheless important that you understand the concept of decimals.
.1 is equal to one tenth; .01 is equal to one hundredth; .001 is equal to one thousandth. Decimals are added and subtracted in the same way ordinary numbers are.
When multiplying decimals, multiply the numbers without decimals; then, push the decimal place to the right once for each time each multiplier is pushed to the right of the decimal.
.05 multiplied by .05 equals .0025, not .25. 6 multiplied by .9 is 5.4, while .6 multiplied by .9 is .54. When in doubt, check these on the calculator.
1. What is .04 multiplied by .08?
2. y is equal to .4(x). If x equals 20, what does y equal?
3. What is the value of .009(.008)(.007)?
Answers to Practice Questions
4(8) is 32. .04 and .08 are both pushed 2 points to the right of the decimal; thus, their product is pushed 4 points to the right.
.4(20) = (20) = 8
The multipliers are each pushed to the right of the decimal 3 times. Thus, we take their product without decimals, and push it to the right 9 times.
9(8)(7) is 504; which pushed to the right 9 times equals 0.000000504.