Answer:
(r-1)d
Step-by-step explanation:
The nth term of any arithmetic series is obtained using the formula:
For any row, r (where r is the number of rows)
The difference between the first and last numbers in any row will be:
Where:
• d=common difference
• r=number of rows.
For an illustration, the difference between the first and last term in the fourth row:
Number of rows = 4
Common difference = 5
Check: 46-31 = 15