The short version A googol is 10100, which is a 1 with 100 zeros written after it. That’s 101 digits in all. The name came from a nine year old. Milton Sirotta made it up for his uncle, the mathematician Edward Kasner, who put it in print in 1940. A googol is bigger than the…
The short version An exponent tells you how many times to multiply a number by itself. In 25, the base is 2, the exponent is 5, and the value is 2 × 2 × 2 × 2 × 2 = 32. Multiplying powers with the same base adds the exponents. Dividing subtracts them. Raising a…
The short version An algorithm is a set of steps that solves a problem the same way every time. Follow the steps and you get the right answer without having to reinvent the method. In school math, “the standard algorithm” means the column methods for adding, subtracting, multiplying, and dividing that kids learn in grades…
The short version Long division repeats four steps: divide, multiply, subtract, bring down. Repeat until there are no digits left to bring down. Whatever is left at the end is the remainder. Write it as R5, as a fraction over the divisor, or keep going with a decimal point. Always check by multiplying: quotient ×…
The short version An even number divides by 2 with nothing left over. An odd number leaves 1 left over. Look at the last digit only. Ends in 0, 2, 4, 6, or 8 and it’s even. Ends in 1, 3, 5, 7, or 9 and it’s odd. This works on a number of any…
The short version The circumference formula is C = 2πr when you know the radius, and C = πd when you know the diameter. Both give the same answer because d = 2r. Use 3.14 for π in most schoolwork, or 22/7 when the numbers divide nicely. A calculator’s π button is more exact. To…
The short version Division splits a total into equal parts. 12 ÷ 4 = 3 means 12 split into 4 equal groups gives 3 in each group. It answers two different questions: how many in each group (sharing), and how many groups fit (grouping). Same math, different story. The vocabulary: the dividend is the total,…
The short version To find a percent of a number, turn the percent into a decimal and multiply. 15% of 80 is 0.15 × 80 = 12. To find what percent one number is of another, divide the part by the whole and multiply by 100. 14 out of 40 is 14 ÷ 40 =…
The short version A polynomial is an expression made of terms added or subtracted together, where every variable has a whole number exponent. 3×2 + 5x – 7 is one. If a variable sits under a square root, in a denominator, or carries a negative or fractional exponent, it isn’t a polynomial. The degree is…
The short version Symmetry means a shape can be moved in some way and end up looking exactly the same as before. The three kinds you’ll meet in school are line, rotational, and point symmetry. Line symmetry is the mirror kind: fold the shape along a line and the halves match. Rotational symmetry means the…