Finding Density of a Floating Block

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To find the density of a floating block, the submerged volume and the weight of the displaced water must be considered. The block's mass can be calculated using the submerged volume, while the density is determined by the total volume of the block. The total weight of the block equals the weight of the water displaced, which is crucial for accurate calculations. The proportion of the block submerged indicates its density relative to water; if it were the same density, it would be fully submerged. Understanding these relationships is key to solving the problem accurately.
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A uniform block of height 0.260 m, floats in water of density 1000 kg/m3. The bottom of the block is 0.2530 m below the surface of the water. What is the density of the block?

fb = mg
m=(pf)(v)
d = m/v

What i did was find the mass, using the volume of what is submerged, then when i found d using equation 3, i used the v of the whole block.
I know I am mixing something up here, but I am not sure what it is..
 
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The total weight of the block must equal the weight of water displaced.
If the block was the same density as water all of it would be under the surface, if it was half the density of water half of it would be below the surface.
What proportion is below the surface?
 
Thread 'Correct statement about size of wire to produce larger extension'

Thread 'Correct statement about size of wire to produce larger extension'

The answer is (B) but I don't really understand why. Based on formula of Young Modulus: $$x=\frac{FL}{AE}$$ The second wire made of the same material so it means they have same Young Modulus. Larger extension means larger value of ##x## so to get larger value of ##x## we can increase ##F## and ##L## and decrease ##A## I am not sure whether there is change in ##F## for first and second wire so I will just assume ##F## does not change. It leaves (B) and (C) as possible options so why is (C)...
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