Test Taking Tip of the Week: Saving Time on the Math Section of Standardized Exams

Some of the standardized tests we encounter, such as the AP Chemistry exam, do not allow use of a calculator on some sections. However, most exams do, so you can rely on the calculator to save time, right? Not necessarily....here are some key tricks you should incorporate into your repertoire to save yourself lots of time on calculations.

1. Memorize the common constants
Some constants appear so often on calculations that you should memorize their approximate values so you do not have to waste precious seconds looking them up. Some examples are:

π ≈ 3.14

e ≈ 2.718
c (speed of light) ≈ 3.0 · 10^8 m/s

R (universal gas constant) ≈ 0.0821 L · atm / K · mol
h (Planck's constant) ≈ 6.63 · 10^-34 J ·s


2. Memorize common formulas
You should not have to look up some formulas. For example:

Area of a circle = πr^2
E = mc^2
PV = nRT
velocity · time = displacement


3. Estimate effectively
You should be able to look at answer choices, or an answer you have calculated, and have an intuitive sense about whether or not the answer "sounds right". For example, if the question is:

Calculate the area of a circle with radius 5 and your answer choices are

(a) 31.46 square units
(b) 15.71 square units
(c) 28.12 square units
(d) 78.54 square units
(e) 97.31 square units

You should be able to estimate the right answer choice is (d) because the area of a circle is πr^2
and 25π is roughly 75 (25 · 3).


4. Use the distributive property to aid in multiplication
Quick! What is 31 x 29? If you're not sure, use the distributive property to reveal:

31 x 29 = 31 x (30 - 1)

It is much easier to add and subtract quickly, so 31 x (30 - 1) = 930 - 31 = 899.

5. Become an expert with powers of 10
Any calculation involving powers of 10 should be automatic. For example, you should be able to quickly perform these calculations without the use of a calculator.

a. 1.17 x 1000 = 1170
b. 75.43 / 10000 = 0.007543
c. 10000 x 100000 = 10^9
d. 4.331 / 0.001 = 4331

If you consistently find yourself running out of time, these techniques should help you!