The "off-peak" weekly average cost of hiring a caravan in Wales is 520. In July the average cost increases to 800. calculate the percentage increase in cost. Give your answer to 2 significant figures.

For this case you can solve the problem by applying a simple rule of three in which we have
 520 ---> 100%
 800 ---> x

 Clearing x we have
 x = (800/520) * 100 = 154%
 the percentage increase in cost was
 154-100 = 54%
 answer
 the percentage increase in cost was 54%