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Work Shown:
18% = 18/100 = 0.18
18% of 24 = 0.18*24 = 4.32
The tip is $4.32
Adding this tip amount onto the original bill leads to 4.32+24 = 28.32
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As a slight shortcut, we can use the multiplier 1.18 to get
1.18*24 = 28.32
This works because
1.18*24 = (1+0.18)*24 = 1*24 + 0.18*24 = 24 + 0.18*24
Notice the portion "24 + 0.18*24" can be found buried in the 1.18*24 expression. I applied the distributive property.
The multiplier 1.18 represents an increase of 18%
We can think of it as
100% + 18% = 1+0.18 = 1.18