A carpenter is constructing a set of stairs. The total rise is 2700 mm and the desired number of risers is 15. What is the individual riser height if all risers are to be equal, and what is the approximate corresponding tread depth using the 17 + 2T rule (where R is riser height and T is tread depth in cm, and the sum should be between 60-64 cm)?

Question: A carpenter is constructing a set of stairs. The total rise is 2700 mm and the desired number of risers is 15. What is the individual riser height if all risers are to be equal, and what is the approximate corresponding tread depth using the 17 + 2T rule (where R is riser height and T is tread depth in cm, and the sum should be between 60-64 cm)?

Answer options: ✅ Riser height: 180 mm, Tread depth: 220 mm

• Riser height: 190 mm, Tread depth: 200 mm
• Riser height: 170 mm, Tread depth: 240 mm
• Riser height: 165 mm, Tread depth: 250 mm

Correct answer: Riser height: 180 mm, Tread depth: 220 mm

Explanation: To calculate the riser height, divide the total rise by the number of risers: 2700 mm / 15 risers = 180 mm. Using the 17 + 2T rule (where R and T are in cm), we convert 180 mm to 18 cm. So, 18 + 2T should be between 60-64 cm. If we take R=18 cm and calculate using 62 as the target, 18 + 2T = 62, so 2T = 44, and T = 22 cm. Thus, a tread depth of 220 mm (22 cm) is appropriate. Other options do not yield the correct riser height or do not satisfy the 17 + 2T rule with the calculated riser height.