<h3>
Answer: 15</h3>
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Explanation using mental math:
He uses 11.5 cherries for his pie, which is half the amount left (after eating those 7 cherries).
This means 2*11.5 = 23 cherries were left over after he ate those seven. In other words, half of 23 is 11.5
If we reverse time, then we get those 7 cherries back to get 7+23 = 30 cherries total. Divide those up equally between the two bags and we get 30/2 = 15 cherries per bag.
Going forward in time we have 15 cherries per bag, so 2*15 = 30 total. He eats 7 to be left with 30-7 = 23 cherries. That cuts in half to 23/2 = 11.5 cherries for his pie.
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Explanation using algebra
c = number of cherries in each bag.
10 < c < 30 based on the second sentence
2c = number of cherries total from both bags combined
2c-7 = the amount left after Chris eats those 7 cherries
(2c-7)/2 = he uses half of the remaining cherries for the pie
Set that equal to the 11.5 number stated and solve for c.
(2c-7)/2 = 11.5
2c-7 = 11.5*2
2c-7 = 23
2c = 23+7
2c = 30
c = 30/2
c = 15
We effectively follow similar steps as when we did the mental math route.
Notice how c = 15 makes 10 < c < 30 true.
