A businessman purchased $35\text{kg}$ of pulse at $\text{Rs. }525$ and sold each kg at the rate of $\text{Rs. }18$. What is his percentage of profit or loss at this?

Given:
Total weight of pulse purchased = $35\text{kg}$
Total Cost Price ($\text{CP}$) = $\text{Rs. }525$

Calculate the cost price per kg:

$$\text{CP per kg}=\frac{525}{35}=\text{Rs. }15\text{/kg}$$

Selling Price ($\text{SP}$) per kg = $\text{Rs. }18\text{/kg}$

Since $\text{SP}>\text{CP}$, it is a profit:

$$\text{Profit per kg}=18-15=\text{Rs. }3\text{/kg}$$

Calculate the profit percentage:

$$\text{Profit Percentage}=\left(\frac{\text{Profit per kg}}{\text{CP per kg}}\right)\times 100=\left(\frac{3}{15}\right)\times 100=20\%$$

Therefore, the businessman makes a $20\%$ profit.