The ratio of koalas to gum trees is 1 : 3. There are 252 gums trees now. Plans are being made to increase this number to 345. Find the expected increase in the number of koalas once the trees are mature, assuming the ratio is unchanged.
To start off you need to find the amount of koalas there are at the current number of trees by using the ratio one to 3 which means there is one koala for every 3 gum trees. So you need to devide 252 by 3 giving you the answer of 84 koalas currently. Now you nees to find how many koalas there are for the future 345 trees based on the same ratio 1 to 3. This would give you 115 koalas to be expected in the future. Finally to find the amount of koalas increaed you need to subtract 84 from 115 giving you a final answer of 31 koalas.