For every acre of grass, the farmer can harvest 560/5 = <<560/5=112>>112 bales of hay each month.

This year, the farmer has 7 + 5 = <<7+5=12>>12 acres of grass.

He can expect to harvest 12 x 112 = <<12*112=1344>>1344 bales of hay per month.

The total hay production this year is 1344*12 = <<1344*12=16128>>16128

From September to December, the farmer would have to feed his horses for a total of 30 + 31 + 30 + 31 = <<30+31+30+31=122>>122 days

Each day his horse eats a total of 3*9 = <<3*9=27>>27 bales of hay.

For the 122 days, the horses will eat a total of 27*122 = <<27*122=3294>>3294 bales.

The total number of bales remaining will be 16128-3294 = <<16128-3294=12834>>12834.

# Answer

12834
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A hay farmer harvested 560 bales of hay from 5 acres of grass per month last year. This year, he planted an additional 7 acres of grass. If the farmer also owns 9 horses and each horse consumes 3 bales of hay a day, how many bales of hay would the farmer have left by the end of December if he starts feeding them this year's hay beginning the first day of September?
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12834
A hay farmer harvested 560 bales of hay from 5 acres of grass per month last year. This year, he planted an additional 7 acres of grass. If the farmer also owns 9 horses and each horse consumes 3 bales of hay a day, how many bales of hay would the farmer have left by the end of December if he starts feeding them this year's hay beginning the first day of September?
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