21A
YOUR ANSWER: 373 watts.
Wrong. But do not despair; we will go over the problem with you.
The problem again was to solve for the input power of a 4-hp motor operating at 80
percent efficiency.
a. Use the correct formula: Efficiency = output x 100.
input
b. Substitute known values 80 = 4 x 746 (watts/hp x 100).
input
c. Multiply both sides by "input"; thus,
80 x input = 4 x 746 x 100 x input.
input
d. "Input" on right side cancels out, and we have
80 x input = 4 x 746 x 100.
e. Divide both sides by 80:
80 x input = 4 x 746 x 100; thus,
80
80
input = 4 x 746 x 100 =
watts.
80
Complete the problem, then continue on to frame 26A.
IT0348
1-22
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