Money is exchanged from one currency into another in a certain ratio, called the exchange rate. The exchange rate of US dollars to British pounds is $1.6:£1. A British pound buys more than 1 US dollar – I suppose that means English people are better than Americans.
To change any amount of dollars into pounds or vice versa, construct a table. To change $60 into pounds, construct the table below.
|
$ |
£ |
|
1.6 |
1 |
|
60 |
x |
The columns or rows are in a certain ratio, so
or
hence
so $60 buys £37.50.
To change £120 into dollars construct the table below.
|
$ |
£ |
|
1.6 |
1 |
|
x |
120 |
The columns or rows are in a certain ratio, so
or
hence
so £120 buys $192.
Suppose there are three currencies – pounds £, dollars $ and Roubles R. £1 buys $1.6 or R56. I guess that means British people are better than Americans but much better than Russians.
I want to change $140 into Roubles.
The £:$:R ratio is 1:1.6:56. The above table becomes
|
$ |
R |
|
1.6 |
56 |
|
140 |
x |
The columns or rows are in a certain ratio, so
or
hence
so $140 buys R4900.