Number sense refers to "a well organised conceptual framework of number information that enables a person to understand numbers and number relationships and to solve mathematical problems that are not bound by traditional algorithms" (Bobis, 1996). In other words, people with number sense can do the following:

Perform calculations in their head

Estimate computations

Judge the relative magnitude of numbers

Recognize part-whole relationships among numbers

Understand place value concepts

Solve problems

So much of science (and life) depends on one’s ability to manipulate numbers that addressing any weaknesses in any one of the above areas is as important as reading and writing.

How to address weaknesses in number sense:

1. Study Khan Academy’s Number Sense lessons: https://www.khanacademy.org/math/on-sixth-grade-math/on-number-sense-numeration. Khan Academy breaks number sense down into six categories:

- Ratios, rates and percentages
- Fractions
- Multiplication and Division
- Place value and decimal operations
- Factors and multiples
- Properties of numbers

Each category contains lessons and practice problems that tailor themselves to your individual progress. And, of course, it’s free.

2. I would add to the list of skills above, learn to:

- Solve algebraic problems for one variable (https://www.khanacademy.org/math/on-sixth-grade-math/on-patterning-algebra#concept-intro)
- Read and interpret graphs (https://www.khanacademy.org/math/algebra-home/pre-algebra/applying-math-reasoning-topic)
- Construct graphs (Plotting and interpreting line equations: https://www.khanacademy.org/math/algebra-home/algebra/two-var-linear-equations)
- Convert among units
- Unit Conversion (https://www.khanacademy.org/math/algebra-home/pre-algebra/rates-and-ratios#unit-conversion)
- Metric System Unit Conversion (https://www.khanacademy.org/math/algebra-home/pre-algebra/rates-and-ratios#metric-system-tutorial)

3. Use your calculator as a last resort. Estimate all answers before plugging numbers in your calculator.

Obviously there are higher-level math courses that you will need to master to become a scientist, such as Trigonometry, Calculus and Statistics, but these are useless without a firm basis in the skills I listed above. Use these fixes to address your number sense issues, and you’ll be calculating with the big girls yet.