I'm looking at JLPT4/5 grammar list and see such grammar point. But I can't find any information about it (truthfully I don't know how to).
Though I found some examples: 1 shuukan ni ikkai - once a week 1 nen ni 3 kai - 3 times a year
Can someone explain this or point me to where I can get that information? Thanks.
Are you asking for help on the pattern, or just other explanations and materials? Because there's not much to it really. You know that に has multiple meanings, including "in" or "within". So it's a pretty straight translation.
<Period> + に + <frequency> → "Within <period>, <frequency> times." or "<frequency> times in <Period>"
- １年に３回 → 3 times within 1 year
- 一週間に１回 → Once per week
