An antique clock cost £540. its price is increased by 18% in a year. what is it now worth?

Well, we don't know how many years we're talking about?

Let's say we want to know the prize after one year: it's 540 +540 * 18%.

another way of writing it is 540* 118%. (this is 637.2)

after two years it will be:

540*118%*118%

we can also write it without =%: (as 100 % is always 1, 101% is 1.01 etc)

540*1.118*1.118

we can also make a more general statement:

n=number of years that have passed:

prize of the clock now=540*