Algebra is integral to eighth-grade math. Building on students' existing knowledge, the teacher introduces students to variables, expressions and equations. Students learn how to solve word problems. For example, they begin to understand that 4 times a number is 40 and can be rewritten as 4x=40. Students also learn how to perform distribution, which means that when letters represent certain numbers, this formula is true: a(b+c)=ab+ac.
Other concepts students master in the eighth grade include fractions, decimals, percents and ratios. They learn how to add, subtract, multiply and divide fractions, round decimals and understand the relationship between decimals and fractions. The teacher also explains to eighth-graders what a ratio is and where people often use them – for example, in cars, as in an engine's compression ratio.
The eighth grade equips students with the skills necessary to perform complex addition, subtraction, division and multiplication. Students learn the order of operations, which specifies which operations should be calculated first. The order of operations is best remembered as PEMDAS, or parentheses, exponents, multiplication, division, addition and subtraction. Students must also learn what integers – including positive and negative – are, as well as even and odd numbers.
Eighth-graders learn how to measure temperature, mass, volume, length and time in the U.S.A. system and metric system. The geometry topics covered in the eighth grade include the Pythagorean theorem, definitions of sin, cosin and tangent and the perimeter and area of a square, rectangle and parallelogram.