OMG! I am 5 foot 8 and i weigh 130 pounds which is 39 kg and 9 stones. I know that you should weigh somewhere between 110 as a low and 120 as a hiegh if you are that tall.

It's a trick question relying on your preconception that feathers are lighter. They of course weigh the same a kg of versus a kg of. Of course it will take a heck of lot more feathers.