ESL Lesson Plans: Decimals, Fractions, and Ordinal Numbers in English
Ordinal Numbers
Begin by second part of the number lesson plan by teaching ESL students how to form ordinal numbers. Ordinal numbers are numbers used for indicating order. The majority of ordinal numbers are formed by affixing the -th suffix onto the cardinal number:
- 1st – first*
- 2nd – second*
- 3rd – third*
- 4th – fourth
- 5th – fifth*
- 6th – sixth
- 7th – seventh
- 8th – eighth
- 9th – ninth*
- 10th – tenth
- 11th – eleventh
- 12th – twelfth*
- 13th – thirteenth
- 14th – fourteenth
- 15th – fifteenth
- 16th – sixteenth
- 17th – seventeenth
- 18th – eighteenth
- 19th – nineteenth
However, note that first (1st), second (2nd), third (3rd), and fifth (5th) are irregular: first (1st) and second (2nd) must simply be memorized, but third (3rd) and fifth (5th) are related to the spelling and pronunciation changes of the cardinal numbers thirteen (13) and thirty (30) and fifteen (15) and fifty (50). Also point out the slight spelling change in ninth (9th) and twelfth (12th).
For multiples of ten, a final y changes to an ie and then the -eth suffix is affixed to the end of the number:
- 20th – twentieth
- 30th – thirtieth
- 40th – fortieth
- 50th – fiftieth
- 60th – sixtieth
- 70th – seventieth
- 80th – eightieth
- 90th – ninetieth
All other numbers above twenty follow the -th suffix rule in combination with the rules for the first nineteen numbers and the multiples of ten. For example:
- 21st – twenty-first
- 100th – one hundredth
- 101st – one hundred and first OR one hundred and oneth*
- 110th – one hundred and tenth
- 1,000th – one thousandth
- 1,111th – one thousand one hundred and eleventh
- 1,000,000 – one millionth
*The use of oneth in higher ordinal numbers is nonstandard but often used by native English speakers.
Decimals
Next introduce the words for the decimals:
- 0.X – tenth(s)
- 0.0X – hundredth(s)
- 0.00X – thousandth(s)
- 0.000X – ten thousandth(s)
- 0.0000X – hundred thousandth(s)
- 0.00000X - millionth(s)
All decimals follow the singular-plural system for English nouns in that the number is spoken as the digit followed by the name of the decimal with any decimal larger than one taking the plural –s marker. A period is placed between the whole number and the decimal. For example:
- 0.1 – one tenth
- 0.2 – two tenths
- 0.01 – one hundredth, one one hundredth
- 0.33 – thirty-three hundredths
- 0.001 – one thousandths, one one thousandth
- 0.654321 – six hundred fifty-four thousand three hundred twenty-one millionths
Decimals may also be spoken as whole number-point-digits. Zeros are spoken as zero or oh. For example:
- 0.1 – point one, zero point one, oh point one
- 1.25 – one point two five
- 6.425 – six point four two five
- 2.1368 two point one three six eight
- 1.057 – one point oh five seven
- 4.0098 – four point zero zero nine eight
Fractions
Finally teach the ESL students how to form fractions in English. The numerator (the top number) is spoken as a cardinal number and the denominator (the bottom number) as an ordinal number. However, half is used in place of second and sometimes quarter in place of fourth. For fractions in which the numerator is larger than one, the denominator takes the plural -s suffix. English fractions are also written with a hyphen between the numerator and denominator. For example:
- 1/2 – one-half
- 1/3 – one-third
- 2/3 – two-thirds
- 1/4 – one-fourth, one-quarter
- 4/5 – four-fifths
- 99/100 – ninety-nine one hundredths, ninety-nine hundredths
Fractions may also be spoken as cardinal number-over-cardinal number. For example:
- 1/2 – one over two
- 1/3 – one over three
- 2/3 – two over three
- 1/4 – one over four
- 4/5 – four over five
- 99/100 – ninety-nine over one hundred
For more information related to numbers in English, please refer to the following Bright Hub articles:
For a printable study sheet of the English cardinal numbers, please download English Ordinal Numbers, Decimals, and Fractions Study Sheet.
Read more: http://www.brighthub.com/education/languages/articles/59563.aspx#ixzz1bWpx136B
¡Ojo!
How many is a billion?
In British English, a billion used to be equivalent to a million million (i.e. 1,000,000,000,000), while in American English it has always equated to a thousand million (i.e. 1,000,000,000). British English has now adopted the American figure, though, so that a billion equals a thousand million in both varieties of English.
The same sort of change has taken place with the meaning of trillion. In British English, a trillion used to mean a million million million (i.e. 1,000,000,000,000,000,000). Nowadays, it's generally held to be equivalent to a million million (1,000,000,000,000), as it is in American English.
Un billón americano son mil millones,
mientras que un billón europeo es un millón de millones.
