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An electrical circuit feeding two single phase motors with a full load current rating of 50 amperes, 30 amperes respectively. Which of the following is the required dual element time-delay fuse size?

A 117.5 amperes

Refer: NEC Table 430.52
The fuse size should be 175% of full load current rating of largest motor plus sum of all other small motors full load current rating.
Dual element fuse size: 1.75 x 50 + 30 = 117.5 amperes