Calculation Basics

A lot of the arithmetic on the test is just substituting given values into a formula or expression and evaluating it carefully.

To substitute, replace each letter with its number, writing the number in brackets so you do not lose a sign, then compute.
The volume of a cylinder is $\pi r^2 h$. With $r = 2$ and $h = 4$:
$\pi (2)^2 (4)$.
Do the power first: $\pi \times 4 \times 4 = 16\pi$.

Follow the order of operations: powers first, then multiplication and division, then addition and subtraction.
For $2lb + 2bw + 2lw$ with $l = 10, b = 5, w = 8$:
$2(10)(5) + 2(5)(8) + 2(10)(8) = 100 + 80 + 160 = 340$.

Take the same care with fractions and decimals. $2 \times \frac{11}{50} = \frac{22}{50} = \frac{11}{25}$, and $12.3 - 12.2 = 0.1$.

The volume of a cylinder is $\pi r^2 h$. Find it when $r = 3$ and $h = 2$.
Substitute: $\pi (3)^2 (2)$.
Square first, then multiply: $\pi \times 9 \times 2 = 18\pi$.

Evaluate $2lb + 2bw + 2lw$ for $l = 4$, $b = 2$, $w = 3$.
Substitute: $2(4)(2) + 2(2)(3) + 2(4)(3)$.
Work out each term: $16 + 12 + 24 = 52$.

What is $2 \times \frac{11}{50}$?
Multiply the numerator by $2$: $\frac{2 \times 11}{50} = \frac{22}{50}$.
Simplify by dividing top and bottom by $2$: $\frac{11}{25}$.