First, we need to find the area of the park:
Area of the park = base x height
Area of the park = 108 ft x 150 ft
Area of the park = 16,200 square feet
We know that the koi pond will cover 1,245 square feet, so the remaining space that needs to be covered with grass seed is:
16,200 square feet - 1,245 square feet = 14,955 square feet
Now we can calculate the number of bags of grass seed needed:
Number of bags = Area to be covered / Area covered by one bag
Number of bags = 14,955 square feet / 7,500 square feet per bag
Number of bags = 1.994
Since we can't buy a fraction of a bag, we need to round up to the nearest whole number. Therefore, Andy will need to buy 2 bags of grass seed to seed the rest of the park.