Step 1:

Class width should be an odd number.

For instance: Get the first class limit add the class width to lowest value.

1435 + 21 = 1456.

Continue the process.

Step 2:

Step 3:

Class boundaries are the midpoints between the upper class limit of a class and the lower class limit of the next class in the sequence.

Each class has an upper and lower class boundary.

For instance : For the first class :1435 - 1456

The lower class boundary is the mid point between 1434 and 1435.

(1434 + 1435)/2 = 1434.5

The upper class boundary is the mid point between 1456 and 1457.

(1457 + 1458) = 1456.5

Cntinue the process.