Mathematical Aptitude: Requires the ability to perform addition, subtraction, multiplication and division; ability to calculate decimals and percentages; may include ability to perform mathematical operations with fractions; may include ability to compute discount, interest, profit and loss, ratio and proportion; and may include ability to calculate surface areas, volumes, weights, and measures. The Metropolitan District Commission (MDC) provides quality water supply, water pollution control, mapping, and household hazardous waste collection to eight member municipalities: Bloomfield, East Hartford, Hartford, Newington, Rocky Hill, West Hartford, Wethersfield and Windsor.