How many terms are there in 20, 25, 30 . . . . . . 140?

Answer: Option B

$$\begin{array}{rl}& \text{Number}\text{of}\text{terms},\\ & =\frac{1^{st}t\text{erm - last}\text{term}}{\text{common}\text{difference}}+1\\ & =\frac{140-20}{5}+1\\ & =\frac{120}{5}+1\\ & =24+1\\ & =25\end{array}$$