Follow these steps (see example):

1. Print out a copy of the 'Erosion-Resistance Index Calulation Table' (printout # Q-6).
2. Determine the 'hardness', inertness, and cohesion values (to two decimal places) for each of the NY City rocks and sediments.
3. Enter these values in columns (a), (b), and (c) of the Erosion-Resistance Index Calculation Table (printout # Q-6).
4. For each material, multiply (a) times (b) times (c) and enter the result in column (d).
5. Round off (d) to the nearest whole number and place the result in column (e). This is the Erosion-Resistance Index.
6. To get the E-R Index for areas underlain by sandstone and shale, calculate the average of the the E-R indices obtained for sandstone and shale individually.
7. Click on the 'Erosion-Resistance Index Checking Table' button to see if your Indices are correct.