The word(s) "fifty" appears 2 time(s) in 2 verse(s) in Quran in Abdullah Yusuf Ali translation.

(1) We (once) sent Noah to his people, and he tarried among them a thousand years less fifty: but the Deluge overwhelmed them while they (persisted in) sin.

(سورة العنكبوت, Al-Ankaboot, Chapter #29, Verse #14)
(Arabic, Transliteration, Urdu (Ahmed Ali), Urdu (Jalandhry), Farsi, Yusuf Ali, Shakir, Picthal, Mohsin Khan, French, Spanish, Indonesian, Malay, German, Bosnian, Russian, Dutch, Italian, Portuguese, Tafsir - Jalal ad-Din, Tafsir - King Fahad Quran Complex)

(2) The angels and the spirit ascend unto him in a Day the measure whereof is (as) fifty thousand years:

(سورة المعارج, Al-Ma'aarij, Chapter #70, Verse #4)
(Arabic, Transliteration, Urdu (Ahmed Ali), Urdu (Jalandhry), Farsi, Yusuf Ali, Shakir, Picthal, Mohsin Khan, French, Spanish, Indonesian, Malay, German, Bosnian, Russian, Dutch, Italian, Portuguese, Tafsir - Jalal ad-Din, Tafsir - King Fahad Quran Complex)