A Guide to the GRE/Decimals

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. Rules 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. Practice 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 1. .0032 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. 2. 8 .4(20) = (20) = 8 3. 0.000000504. 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.