Introduction to Decimals Section 5.1 Introduction to Decimals

Decimal Notation Used to denote a part of a whole. Numbers written in decimal notation are called Decimal Numbers, or simply Decimals. The decimal number has three parts. Whole Number Part Decimal Part Decimal Point

Write a Decimal in Words Steps Write the whole number part Change decimal to the word ‘and’. Write the decimal part as a whole number. End with the place value of the last digit.

Example Translate the decimal into words. 2,573.1984

Example Translate the decimal into words. 12.0235

Write the Words in Decimal Format Steps Find the word and, translate it into a decimal. Translate the words before and as a whole num. Find the last word on the right side of and, that is the number of spaces you need to fill. Translate the words after and, into the spaces you have created.

Example Translate the word into decimals. Fourteen thousand twenty-two and six hundred millionths.

Example Translate the word into decimals. Two hundred fifteen and two hundred fifteen hundred thousandths.

Decimal → Fraction Steps Move whole number to the side, a Count the number of places after the decimal, n Place decimal number (without decimal) in the numerator. The denominator will be a 1 with n zeros. Simplify the fraction Bring whole number back in, a.

Example Write -12.35 in fraction form.

Example Write -9.052 in fraction form.

Example Write 0.25 in fraction form.

Comparing Decimals Compare digits in the same places left to right. When two digits are not equal, the number with the larger digit is the larger decimal. If necessary, insert 0s after the last digit of the decimal point to continue comparing.

Example Insert < , > or = to form a true statement. 0.00985 0.0098

Example Insert < , > or = to form a true statement. 0.0985 0.09850

Rounding Decimal Steps Locate the digit of the place value given. Look at the number to the right If the number is a 0, 1, 2, 3 or 4 leave the digit alone. If the number is 5, 6, 7, 8 or 9 add one to the digit Replace all the numbers to the right of the given digit with zeros.

Example Round 0.64 to the nearest tenth.

Example Round $5.78 to the nearest dime.