32 shirt pieces of 120 cm each can be cut from a reel of cloth. After cutting these pieces 80 cm of cloth remains. What is the length of reel of cloth in metres?

### Concept & Strategy To find the total length of the cloth reel, we must calculate the total length of all the cut pieces combined and add the remaining cloth length. $$Total\ Length = (Number\ of\ Pieces \times Length\ per\ Piece) + Remaining\ Length$$ ### Step-by-Step Solution * **Given:** * Number of shirt pieces = 32 * Length of each piece = 120 cm * Remaining cloth = 80 cm * **Calculation:** 1. Calculate the total length of the cut pieces: $32 \times 120 = 3840$ cm 2. Add the remaining cloth to find the total length of the reel in cm: $3840 + 80 = 3920$ cm 3. Convert the total length from centimeters to meters (since 100 cm = 1 m): $3920 / 100 = 39.20$ meters ### Exam Strategy & Shortcut Instead of full multiplication, use the unit digit method to quickly verify the answer. The unit digit of $32 \times 120$ ends in a $0$. Focusing on the tens digit: $2 \times 2 = 4$. So the product ends in $40$. Adding the remaining $80$ cm: $40 + 80$ yields a value ending in $20$. Checking the options for a decimal ending in $.20$, option (b) is the clear match. ### Common Pitfall Students often forget to convert the final answer from centimeters to meters, incorrectly choosing a distractor like 3920 if it was not specified with units. Always check the required unit in the final question sentence. ### Final Answer **Therefore, the correct answer is 39.20 metres.**