For 0 to 6 minutes, A = 4t + 1 and B = 2t + 7 give total liters. A has the greater change rate. At one minute, A has 5 liters while B has 9 liters; the greater rate does not make A greater at every time. Equality is 4t + 1 = 2t + 7, so 2t = 6 and t = 3 minutes. Each then has 13 liters.
Your new practice
For 0 to 6 minutes, supplied models C = t + 12 and D = 3t + 2 give total liters. A fictional learner says: “C starts higher, so C always has more.” Compare rates, amounts at minutes 1 and 6, and the equality time. Explain when the learner’s claim fails within the stated domain.
Your comparisons, equality and qualified conclusion