Final answer:
To measure 11 cm using rods of 5 cm, 7 cm, and 9 cm, align the 5 cm and 7 cm rods to make 12 cm. Then overlap them with the 9 cm rod to subtract 1 cm, leaving you with the desired 11 cm length.
Step-by-step explanation:
To measure a length of 11 cm using rods that are 5 cm, 7 cm, and 9 cm long, you can perform a simple addition operation with these rods. Here is how you can do it:
- First, take the 7 cm rod and the 5 cm rod.
- Align them end to end without overlapping.
- The combined length of these rods will be 12 cm (since 7 cm + 5 cm = 12 cm).
- Now you need to measure 1 cm less to get 11 cm.
- Take the 9 cm rod and align it with one of the combined rods, so that only 1 cm of the combined rods extends beyond the length of the 9 cm rod.
- The extended part will be 1 cm, because when you subtract 9 cm (the length of the third rod) from 12 cm (the combined length of the first two rods), you get 3 cm.
- Finally, you subtract this excess 1 cm length from the 12 cm by considering the portion of the combined rods that aligns with the 9 cm rod, which gives you the desired 11 cm length.
This method demonstrates a practical application of adding and subtracting lengths to achieve a specific measurement.