Since we're after three numbers that multiply together, a good place to start is the cube root of 1,287, which is 10.88 (2 dp).
We quickly find that the numbers must be 9, 11 and 13.
Which is heavier, a kilo of feathers or...
...a kilo of steel?
[Puzzle Code = ZSOU]
Direct Link: www.brainbashers.com?ZSOU
Hint: This is a Gotcha.
Answer: They weigh the same.