Keep the physical model and the measurement together
A scientific calculation begins with a model and its conditions. Before using a formula, identify the system, the relevant variables and what is held constant. Ohm's law relates current, voltage and resistance for the stated circuit model; a battery's internal resistance requires distinguishing its electromotive force from its terminal voltage. In mechanics, momentum and kinetic energy are different quantities, so a collision can conserve one while reducing the other. Chemical amounts require a balanced equation and a check of the limiting reactant before a product amount is calculated. A gas-law problem uses absolute temperature and a consistent pressure ratio. Biology questions often ask about a process or structure rather than a calculation: distinguish the role of a ribosome, a membrane channel and an energy-carrying molecule. Draw a short causal chain and check whether a distractor reverses it. These exercises sample physics, chemistry, biology and a little earth science; they are a foundation bank, not complete coverage of every science subject.