Interchange two numbers in the equation to make it correct: 36 x 11 / 3 − 10 + 4 = 49

(from left to right):
$36 \times 11 = 396$
$396 \div 3 = 132$
So the equation becomes:
$132 - 10 + 4$

(from left to right):
$132 - 10 = 122$
$122 + 4 = 126$

Currently, the equation is $126 = 49$, which is incorrect. We need to find an interchange of two numbers that makes the left side equal to 49.

Let's test each option:

Option 1: Interchange 10 and 4
The equation becomes:
$36 \times 11 \div 3 - 4 + 10$

1. $36 \times 11 = 396$
2. $396 \div 3 = 132$
3. $132 - 4 = 128$
4. $128 + 10 = 138$ Since $138 \neq 49$, this option is incorrect.

Option 2: Interchange 4 and 11
The equation becomes:
$36 \times 4 \div 3 - 10 + 11$

1. $36 \times 4 = 144$
2. $144 \div 3 = 48$
3. $48 - 10 = 38$
4. $38 + 11 = 49$ Since $49 = 49$, this option is correct.

Let's quickly check the other options to confirm.

Option 3: Interchange 49 and 36
This option suggests swapping the target value (49) with a number in the expression (36). If we interpret this as making the left side equal to 36, it would be:
$49 \times 11 \div 3 - 10 + 4$
$539 \div 3 - 10 + 4$
This will not result in an integer, and certainly not 36. This option is incorrect.

Option 4: Interchange 11 and 3
The equation becomes:
$36 \times 3 \div 11 - 10 + 4$

1. $36 \times 3 = 108$
2. $108 \div 11$ is not an integer ($108/11 \approx 9.81$). This will not result in 49. This option is incorrect.

Therefore, interchanging 4 and 11 makes the equation correct.

The final answer is $\text{2}$