At 15, you may still have some growing to do, so, I think it's better to be a few pounds heavy than a few pounds light (else undernourishment could lead to your adult height being less than your potential).
(change to North American cuisines is why 2nd generation Asians are so much taller than their parents, so I do think 15's too young a time to risk being underweight)
It depends on your frame size. If you have larger frame, you're likely to weigh more than if you're smaller framed.
As long as you're active, 48 kg is okay for a 15 yr old.
Female, can't really check, 108 pounds/7.7 stone
Male or female? Waist measurement? How many pounds in a stone?