A solid of R.D. 4.2, is found to weigh 0.200kgf in air

Question

Find its apparent weight in water

Answer 1

If the relative density is 4.2 compared to water, then in water it will weigh the same amount less the weight of the water displaced.

Example:

if the volume is 1m^3, with RD 4.2, then its weight is 4200N. In water, its apparent weigh is 4200N-1m^3*1E3kg*9.8= 4200-980=3400N

I wonder if you are learning kgf as force, instead of using the SI unit of Newtons.