Two numbers are in a ratio of 5:4. Their sum is 720. Find the bigger number.

So the numbers are x and y

x:y=5:4

x/y=5/4

this means that x is worth 5 units and y is worth 4 units so

x:y=5:4, therefore it can be represented by

x:y=5z:4z

we know that they add to 720

720=5z+4z

add like terms

720=9z

divide by 9

80=z

multiply by 4

320

80=z

mutipply by 5

400

the numbers are 400 and 320