How much is a Kikar? Why does the Torah reckon one thousand, seven hundred and seventy-five Shekalim as a partial Kikar?
What did they do with any silver that was donated voluntarily?
Rashi (in Terumah): They used it to manufacture K'lei Shareis.
Da'as Zekeinim, Hadar Zekenim and Moshav Zekenim: The voluntary silver went to a storehouse for Bedek ha'Bayis and towards the needs of the Tzibur and for Korbanos Kayitz ha'Mizbe'ach - Moshav Zekenim).
Why does the Torah say "Kesef Pekudei ha'Eidah", and not 'Kesef ha'Terumah' or 'ha'Tenufah', like it says about the gold and copper?
Da'as Zekenim: Because the Torah only mentions the amount of silver that was obligatory (a half-Shekel for each man). It does not mention how much they gave voluntarily.