SOLUTION:The centre of GRAVITY(G) of the wooden BLOCK lies at its midpoint that is at 0.5l from the bottom of the block..Let the block is IMMERSED upto a height 'x', then the centre of buoyancy(B) will be at 0.5x from the bottom of the block.Now the distance between centre of gravity and centre of buoyancy(GB) is 0.5(l - x)From the given,0.5(l - x) = 0.15l ⇒ x = 0.7lNow the immersed height is 0.7lEquating buoyant force and weight,ρb × A × l × g = ρw × A × 0.7l × g\(\Rightarrow \frac {\rho _b }{\rho _w}=0.7\)∴ Specific gravity of wooden block is 0.7