If the standard deviation of a set of numbers is 3.6, what is the variance?

Analyze the question You're given the standard deviation (3.6) and asked for the variance.

Concept Variance is the square of the standard deviation:

Variance = (Standard deviation)²

Equivalently, standard deviation = √Variance.

Solution Variance = (3.6)²

Calculate 36 × 36 = 1296, so 3.6 × 3.6 has two decimal places in total:

(3.6)² = 12.96

You can also check it this way:

• 3.6 × 3 = 10.8
• 3.6 × 0.6 = 2.16
• 10.8 + 2.16 = 12.96

Answer The variance is 12.96, which is option A.

Tip Standard deviation and variance are linked by squaring and square rooting. If a question gives you one, just square it to get the variance, or take the square root to go from variance back to standard deviation. Also, always count decimal places: one decimal place squared gives two decimal places (3.6 → 12.96), which helps you quickly rule out options like 12.9 (only one decimal place).