Answer:
- $125
- $65, $65, $65 -- they are all the same
Step-by-step explanation:
The quantity of food required for the two cats for one day is ...
(3/4 can) + (1/2 can) = (3/4 +2/4) can = 5/4 can
Then the cost per day for cat food is ...
$5/(3 cans) × (5/4 can/day) = $25/12 /day
We note that the cost for some number of days will be the product of this factor and the number of days, rounded up to the next higher $5.
1. The cost for 60 days is ...
(60 days)($25/12 /day) = $25 × 60/12 = $125
A 60-day supply of cat food costs $125.
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2. A 29-day supply costs ...
(29 day) × $25/12 /day = $60 5/12, rounds up to $65 for 29 days
A 30-day supply costs ...
(30 day) × ($25/12 /day) = $62.50, rounds up to $65 for 30 days
A 31-day supply costs ...
(31 days) × ($25/12 /day) = $64 7/12, rounds up to $65 for 31 days.
These costs are all the same.
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3 cans last, on average, 2 2/5 days. That means some purchases of 3 cans will last for 2 days, and some will last for 3 days. It so happens that the purchase made to cover day 29 will also cover day 30 and day 31.
