My question is: Reagan's school has a fish tank with a total of 280 fish of two types, koi fish and goldfish. Over the next 3 weeks, the school added 2 koi fish and 5 goldfish per day. If the tank had 200 goldfish at the end of the three weeks, what's the total number of koi fish in the tank after the three weeks? Your thoughts:
The total number of days in 3 weeks is 3 * 7 = 21 days. If 2 koi fish are added every day, the total after 21 days is 21 * 2 = 42 koi fish. if 5 goldfish are added every day, the total after 21 days is 5 * 21 = 105 goldfish. The total number of fish in the tank after 3 weeks is 280 + 42 + 105 = 427 fish. If there were a total of 200 goldfish in the tank after 3 weeks, then the number of koi in the tank is 427 - 200 = 227 koi fish. The final answer: 227.