Answer:
8) -0.05 lb/day . . . . or . . . . -1.5 lb/month
10) 43.6%
Explanation:
8) Using the given units, the "unit rate" is the rate expressed with a denominator of 1. For rates involving time, usually the time period is in the denominator. That is, we're interested in what happens in a unit of time.
... (change in pressure)/(change in time) = (-1.5 lb)/(30 day) = -0.05 lb/day
You can recognize that 30 days is a month, so we could just change the 30 day period to 1 month. Then the denominator will be 1 unit as desired.
... (change in pressure)/(change in time) = (-1.5 lb)/(1 month) = -1.5 lb/month
(My guess is that this latter solution may not fly.)
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10) 34/78 × 100% = 43.589743_589743% . . . . a repeating decimal with a 6-digit repeat
... ≈ 43.6%
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Comment on unit rates involving time
Sometimes, we're interested in the amount of time to do a task. Then the unit rate is expressed as "time per task", rather than "tasks per time".
In the above problem, we might be interested in the amount of time it takes to lose 1 lb of air pressure. Then the unit rate would be 20 days/lb.
Other kinds of unit rates can be inverted similarly, often for similar reasons.