Patrick bought 2 tickets at $100.00 each for a total of 2*100 = $<<2*100=200.00>>200.00
The oldest son went 35 times and the youngest went 15 times for a total of 35+15 = <<35+15=50>>50 trips
The tickets cost $200.00 and together, the boys went to the park 50 times so each trip cost 200/50 = $<<200/50=4.00>>4.00
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