1. Problem: Calculate the speed of the train and the time to cover 400 km. Step 1: Given speed calculation $$\text{Speed} = \frac{180}{4.5} = 40\ \text{km/h}$$ Step 2: Calculate time to cover 400 km $$\text{Time} = \frac{\text{Distance}}{\text{Speed}} = \frac{400}{40} = 10\ \text{hours}$$ Final answer: The train travels at 40 km/h and takes 10 hours to cover 400 km. 2. Problem: Construct triangle PQR with sides 5 cm, 4 cm, and 6 cm. Step 1: Draw segment PR of length 6 cm. Step 2: Using P as center, draw an arc with radius 5 cm. Step 3: Using R as center, draw an arc with radius 4 cm intersecting the arc from P at Q. Step 4: Join points P to Q and R to Q to form triangle PQR. Final answer: Triangle PQR is constructed with sides 5 cm (PQ), 4 cm (RQ), and 6 cm (PR).