Evaluate:

​$$(0.2)^3-(0.02)^3$$​​

Correct option is C

Given:

(0.2)³- (0.02)³

Formula Used:

$$a^3 - b^3 = (a - b)(a^2 + ab + b^2)$$

​Solution:

(0.2)^3​ - (0.02)³=  (0.2-0.02) [(0.2)^2​ + (0.2)(0.02) + (0.02)²

= 0.18[0.04 + 0.004 + 0.0004]

= 0.18$$\times$$ 0.0444

= 0.007992

Thus, option (C) is right.

Alternate Method:

$$\text{Calculate } (0.2)^3: \\(0.2)^3 = 0.2 \times 0.2 \times 0.2 = 0.008 \\\text{Calculate } (0.02)^3: \\(0.02)^3 = 0.02 \times 0.02 \times 0.02 = 0.000008 \\\text{Subtract the two values:} \\(0.2)^3 - (0.02)^3 = 0.008 - 0.000008 = 0.007992 \\\therefore (0.2)^3 - (0.02)^3 = 0.007992$$

Thus, option (C) is right.

(Average Salary=Sum of salaries over 5 yearsNumber of years\text{Average Salary} = \frac{\text{Sum of salaries over 5 years}}{\text{Number of years}}