How much?

One question - How much money to carry to travel?
This began with a  need to know how much money to carry while traveling by train with a group? Initially, each one came up with - 1000, 200, 400, 200o and so on. Then we broke our journey  - How much do we pay for the cab? How many tickets? How much is one ticket? How many times do we travel? Just a small detailing led to understanding and coming up with a mathematical figure for our travel budget. 
 
How do we decide how much money to carry?
How much minimum to keep in the pouch?
How much do we spend every week?
What does the cab cost?
What is the cost of train tickets?
 
We all know maths, we all knew addition - One questions and further exploration led to applying that knowledge thoughtfully.