This is a narrative of a classroom episode in which students could see how mathematics can help someone avoid some common mistakes and take a right decision. A simple question involving ratios and simultaneous linear equations could do this with right learning strategy. Students were given a question to work on, and the discussion build on that as given below. A class was working on the following problem: A vendor makes two types of milkshakes using milk and syrup. The ratio of these two ingredients in two types of Shakes is given as - ShakeX, milk : syrup = 2 : 3   - ShakeO, milk : syrup = 3 : 4   He has 23 liters of milk and 31 liters of syrup.   How much of each shake should he prepare so that everything is used? The discussion went like:  We assume he prepares (x) liters of ShakeX and (y) liters of ShakeO,  It was noted: - Each shake consumes some milk and some syrup   - Total milk used must become 23 liters   - Total syrup used must become ...