Introduction:
To determine how many kilograms of rice can be bought for a certain amount of money, we need to divide the given amount by the price per kilogram of rice.

Given:
- Price of 1 kg rice = rupees 34 1/4
- Amount of money available = rupees 680 1/2

Step 1: Convert the price of 1 kg rice to a decimal:
To simplify calculations, we need to convert the mixed fraction price of rice into a decimal.
- rupees 34 1/4 = rupees 34.25 (since 1/4 is equal to 0.25)

Step 2: Divide the amount of money available by the price per kilogram:
To find the number of kilograms that can be bought, we divide the amount of money available by the price per kilogram.
- rupees 680 1/2 ÷ rupees 34.25 = 20

Answer:
- The number of kilograms of rice that can be bought for rupees 680 1/2 is 20 kg.

Explanation:
To understand why we divide the amount of money by the price per kilogram, we can think of it as finding the number of times the price per kilogram can be subtracted from the given amount of money.
- In this case, the price per kilogram is rupees 34.25, and we have rupees 680 1/2 available.
- We subtract rupees 34.25 from the total amount until we can no longer do so without going below zero.
- After 20 subtractions, we will have used up all the money, and the remaining value will be zero.
- This means that we can buy 20 kilograms of rice for rupees 680 1/2.

Conclusion:
By dividing the given amount of money by the price per kilogram, we find that 20 kilograms of rice can be bought for rupees 680 1/2.

20 kg