Ordinal and quantitative numerals - usage of case endings

[oryx_and_crake]

Many people (even the native speakers) have problems with these, so the following might be helpful.

For ordinal numerals written with numbers you should use case endings.
Example: 1-я, 2-й, 5-й, 10-го
You should not use the entire ending (i.e. 3-его or 5-ому is wrong).
The rule goes as follows:
If the one-before-last letter of the ending is a vowel, use one, the last letter of the ending: 1-й день, в 10-й части;
If the one-before-last letter of the ending is a consonant, use two last letters of the ending: 1-го вида, 10-му посетителю.
Do not use anything in dates: 25 апреля 1980 года.

For quantitative numerals written with numbers CASE ENDINGS ARE NOT USED.

DO NOT EVER write anything like "25-ти" or "4-тыре", or even "5ять".