To find the unit rate per kilogram of mangoes, divide the total cost by the number of kilograms:

$\text{Unit rate per kilo} = \frac{150}{3} = 50$

Thus, the vendor sells mangoes at 50 per kilogram.

Would you like a detailed explanation or have any questions?

Here are 5 related questions you might find helpful:

1. If the vendor sold 10 kilos of mangoes, what would the total cost be?
2. What would the cost be for 5 kilos of mangoes?
3. If the price increased to 60 per kilogram, what would be the total cost for 3 kilos?
4. How many kilos of mangoes can you buy with 300 at the current unit rate?
5. If a customer buys 7 kilos, how much will they pay at the current rate?

Tip: To find unit rates, always divide the total by the quantity.