How to remember
The kanji 十 is a simple cross, which visually represents the number ten, or can be imagined as tally marks for ten items. 'とお' — Imagine seeing TEN TOES sticking out from under a blanket. 'じゅう' — Sounds like 'JUICE'. You have ten bottles of juice. Vocabulary
十日とおか
tenth day of the month, ten days