Area of the wet surface  = [2(lb + bh + lh)  lb] 
= 2(bh + lh) + lb  
= [2 (4 x 1.25 + 6 x 1.25) + 6 x 4] m^{2}  
= 49 m^{2}. 
Volume of water displaced  = (3 x 2 x 0.01) m^{3} 
= 0.06 m^{3}. 
∴ Mass of man  = Volume of water displaced x Density of water 
= (0.06 x 1000) kg  
= 60 kg. 
Number of bricks =  Volume of the wall  =  ❨  800 x 600 x 22.5  ❩  = 6400. 
Volume of 1 brick  25 x 11.25 x 6 
Clearly, we have r = 3 cm and h = 4 cm.
∴ Volume =  1  Πr^{2}h =  ❨  1  x Π x 3^{2} x 4  ❩cm^{3}  = 12Π cm^{3}. 
3  3 
Πr^{2}h  =  924  ⟹ r =  ❨  924  x 2  ❩  = 7 m. 
2Πrh  264  264 
And, 2Πrh = 264 ⟹ h =  ❨  264 x  7  x  1  x  1  ❩  = 6m. 
22  2  7 
∴ Required ratio =  2r  =  14  = 7 : 3. 
h  6 
So, l = √(7)^{2} + (14)^{2} = √245 = 7√5 cm.
∴ Total surface area  = Πrl + Πr^{2}  


= [154(√5 + 1)] cm^{2}  
= (154 x 3.236) cm^{2}  
= 498.35 cm^{2}. 
∴ Rise in water level =  ❨  200  ❩m 0.25 m = 25 cm. 
40 x 20 
Radius =  1  mm  =  1  cm.  Then, 
2  20 
⟹  22  x  1  x  1  x h = 66. 
7  20  20 
⟹ h =  ❨  66 x 20 x 20 x 7  ❩  = 8400 cm = 84 m. 
22 
⟹ h =  180  m =  20  m. 
27  3 
∴ Volume =  ❨  15 x 12 x  20  ❩m^{3}  = 1200 m^{3}. 
3 
Then, [(330  10) x (260  10) x (110  x)] = 8000 x 1000
⟹ 320 x 250 x (110  x) = 8000 x 1000
⟹ (110  x) =  8000 x 1000  = 100 
320 x 250 
⟹ x = 10 cm = 1 dm.
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