Translation:My grandmother is 101 years old.
According to the website that I checked, it should be issai.
一歳 【いっ・さい】 – 1 year old
八歳 【はっ・さい】 – 8 years old
十歳 【じゅっ・さい】 – 10 years old
二十歳 【はたち】 – 20 years old
You would only ever use そぼ for your own grandmother, but おばあさん you would use to refer to everyone else's grandmother (or your own if you were being strategically polite ; ) ). おばあさん and おじいさん are also commonly used to address elderly men and women who you might not know at all.
Is it? I kept saying this sentence to myself without "and", and it seems that I keep putting in a "en" sound really fast between "hundred" and "one", almost meshed in after the last d in "hundred". I assume that the "en" sound that I keep putting in would be some form of degenerate "and". If I slow down and pronounce each word clearly in "hundred one" in this sentence on grandma's age, it feels way weird... but if I was to say "A hundred one years ago...", that seems fine off of my tongue. But whether that is just a Washington thing or not, I don't know.
tl;dr I think "and" of some form is needed if we are talking about the age of something, but is not needed in any other case (like calander year or the like)... but I don't really know, just a guess
Plenty of languages have 'and' in their numbers. English - one hundred and one. Spanish - diez Y seis. Maori - tekau MA waru. Not all languages translate that 'and' but that doesn't mean that it isn't necessary or that it's optional. Here we are translating Japanese to English and English includes that 'and'. It is necessary.
I would myself write 101 with the and. but not being an English native speaker, I looked on numerous websites about writing number rules. it seems that most of people writing without and are likely Americans.
When writing out a number of three or more digits, the word and is not necessary. However, use the word and to express any decimal points that may accompany these numbers. (grammarbook.com)
I'm just saying that writing with or without and can be both accepted, depending on where you live.
N.B. sixteen in Spanish is dieciséis, not diez y seis.
That depends if its English English or American English we're learning here. In American its 100% acceptable to leave out the "and". Much like it is when they say "I'm going to write you" instead of "... write to you". Or "I could care less" instead of "I couldn't care less". They're not wrong, it's just American variations of English.