One large box of birdseed can feed half a dozen parrots for 15 days. For how many days can this same large box of birdseed feed 5 parrots.

Box = b

Parrots = p

b/p = number of days it can support the parrots

Half a dozen = 6 (A dozen is 12)

1/6 = 15

To work out the percentage of '6' '5' is, use the equation

(5/6) * 100 = 83.333 ...

Meaning that with one less bird, the box will support the birds for 16.666 ... (100 - 18.333 ...) longer

(15/100) * 116.666 ... = 17.4999 ...

The box will sustain the parrots for 17.5 days