Given Information:
- The shopkeeper gains 1 rupee on each pen.
- The shopkeeper loses 40 paise (0.40 rupees) on each pencil.
- The shopkeeper sells 45 pens and some pencils.
- The total loss incurred by the shopkeeper is 5 rupees.

Let's solve the problem step by step:

Step 1: Calculate the loss on each pen:
- The shopkeeper gains 1 rupee on each pen, which means the cost price of each pen is 1 rupee less than the selling price of each pen.
- Therefore, the loss on each pen is 1 rupee.

Step 2: Calculate the loss on each pencil:
- The shopkeeper loses 40 paise (0.40 rupees) on each pencil, which means the cost price of each pencil is 40 paise more than the selling price of each pencil.
- Therefore, the loss on each pencil is 40 paise (0.40 rupees).

Step 3: Calculate the total loss on pens:
- The shopkeeper sells 45 pens, and the loss on each pen is 1 rupee.
- So, the total loss on pens is 45 rupees (45 pens * 1 rupee/pen).

Step 4: Calculate the total loss on pencils:
- Let's assume the shopkeeper sells 'x' pencils.
- The loss on each pencil is 40 paise (0.40 rupees).
- So, the total loss on pencils is 0.40 rupees * x pencils.

Step 5: Calculate the total loss:
- The total loss incurred by the shopkeeper is 5 rupees.
- Therefore, the total loss on pens and pencils should be equal to 5 rupees.
- Total Loss = Total Loss on Pens + Total Loss on Pencils
- 5 rupees = 45 rupees + (0.40 rupees * x pencils)

Step 6: Solve for 'x' (number of pencils sold):
- Subtracting 45 rupees from both sides of the equation, we get:
- 5 rupees - 45 rupees = 0.40 rupees * x pencils
- -40 rupees = 0.40 rupees * x pencils

- Dividing both sides of the equation by 0.40 rupees, we get:
- -40 rupees / 0.40 rupees = x pencils
- -100 pencils = x pencils

Step 7: Interpret the result:
- The negative value of 'x' implies that the shopkeeper did not sell any pencils. However, this contradicts the given information that the shopkeeper sells some pencils.
- Therefore, there must be an error in the calculations or the given information.

Conclusion:
- Based on the given information and the calculations, it seems that there is an inconsistency or error in the problem statement. The calculation suggests that the shopkeeper did not sell any pencils, which contradicts the fact that the shopkeeper sells some pencils. Further clarification or correction is required to determine the number of pencils sold.