Algebra is solving for the unknowns by equation manipulations. For example, watts equals volts times amps. Suppose a machine requires 1,000 watts of power. You have 240 volts at the source. The unknown is how many amps of current draw is produced, so you can size a breaker. Solving the equation yields 4.167 amps of draw. This is a very simple equation. Many complex equations fill up an entire sheet of paper. The Viterbi School of Engineering at the University of Southern California requires strong algebra skills, in order to pass the placement exams.
Trigonometry deals with triangles, and all associated equations. The functions of sine, cosine and tangent all deal with the interrelationships between the length of the sides. The most famous equation, Pythagorean's Theorem, is A squared plus B squared equals C squared. Engineers use trigonometry constantly in their work -- for instance, to find the correct length of a lever.
Geometry deals with shapes; such as circles, cylinders, and cones. Since engineers design shapes, they must know all the associated equations. For example, they must figure out the volume of a cylinder, since a car engine uses cylinders. Carleton college states the Math 244 geometry class is a requirement for all engineering students.
Statistics is more than just reading facts printed out by some survey company. Statistics deal with probabilities, exact population group numbers, and the exact outcome of an experiment. It also deals with quality control issues, and how the quality of products is determined. For example, gloves are mass produced. Defects aways arise in the right thumb tip. Statistics evaluates the defects, and engineers develop solutions, based upon statistics. The Math 265 class, required for all engineering students at Carleton College deals specifically with probabilities.