**Given information:**
- Mean of the weekly wages = Rs. 700
- Standard deviation of the weekly wages = Rs. 50

**To find:**
- Expected number of workers with wages between Rs. 660 and Rs. 720

**Approach:**
To find the expected number of workers with wages between Rs. 660 and Rs. 720, we need to calculate the area under the normal distribution curve between these two values.

**Step 1: Standardize the values**
To standardize the values, we use the formula:
z = (x - μ) / σ
where z is the standard score, x is the value, μ is the mean, and σ is the standard deviation.

For Rs. 660:
z1 = (660 - 700) / 50 = -0.8

For Rs. 720:
z2 = (720 - 700) / 50 = 0.4

**Step 2: Find the area under the curve**
To find the area under the curve between these two z-scores, we can use a standard normal distribution table or a calculator.

Using the standard normal distribution table, we find the area to be 0.7881 for z1 and 0.6554 for z2.

**Step 3: Calculate the expected number of workers**
The expected number of workers with wages between Rs. 660 and Rs. 720 can be calculated using the formula:
Expected number = Total number of workers * (Area between z1 and z2)

Given that there are 5000 workers in the factory, we can calculate the expected number as follows:
Expected number = 5000 * (0.6554 - 0.7881)

Calculating the above expression:
Expected number = 5000 * (-0.1327)
Expected number = -663.5

Since the expected number of workers cannot be negative, we can conclude that there would be approximately 664 workers with wages between Rs. 660 and Rs. 720.

Therefore, the expected number of workers with wages between Rs. 660 and Rs. 720 is approximately 664.