Percent and ratio questions are fast with multipliers. Unit conversion questions are fast when you write units as fractions that cancel.
Work through it
After a 20% discount, a shirt costs $48. Find the original.
Sale is 80% of the original.
Divide.
Price rises 10%, then falls 10%. Net change?
Multiply.
It's lower.1% decrease
Convert 72 km/h to m/s.
Change km to m.
Change hours to seconds.
Result. m/s
Watch out for this
After 20% off, adding 20% to get back the original.
20% of a smaller number isn't enough. Divide by 0.8 instead.
The short version
Percent change is the change divided by the original. Keep units in the same position, and convert units step by step.
Percent change is the change divided by the original. Keep units in the same position, and convert units step by step.
Your turn
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