How many 7490 ICs are to be cascaded to count up to 999?

Likewise, if we wanted to count from 0 up to 999 (0000 0000 0000 to 1001 1001 1001), then three cascaded decade counters are required. In fact, multiple decade counters can be constructed simply by cascading together individual BCD counter circuits, one for each decade as shown. 2-digit BCD Counter from 00 to 99