Rate

Every time a bus timetable promises you'll reach Colombo in three hours, every time you glance at a fuel gauge and wonder if you'll make it home, every time a water tank fills for the morning — a rate is doing the work. A rate is the single most useful idea in everyday maths, because it links two different measurements — distance and time, litres and minutes, rupees and hours — into one number you can plan your day around. Master it now and speed, flow, graphs and "how long will it take?" problems all become the same simple calculation.