A woman travelled at a speed of 20 m/min

Step 1: Find total distance

Distance covered in first part:

$20 \times 90 = 1800$ m

Distance covered in second part:

$72 \times 66 = 4752$ m

Total distance:

$1800+4752=6552$ m

Step 2: Find total time

Total time:

$90+66=156$ min

Step 3: Calculate average speed

Average speed:

$\frac{6552}{156}=42$

Final Answer: 42 m/min