6 A closed cylindrical water tank is made from a plastic sheet Its diameter is 1 4m and - Maths - Surface Areas and Volumes

Question

6   A   c l o s e d   c y l i n d r i c a l   w
a t e r   tan k   i s   m a d e   f r o m
  a   p l a s t i c   s h e e t   I t s  
d i a m e t e r   i s   1 4 m   a n d   h e i g
h t   3 5 m   F i n d     ( i )   L a t e
r a l   ( c u r v e d )   s u r f a c e   a r e a
  o f   t h e   tan k     ( i i )   a
c t u a l   a r e a   o f   t h e   p l a s t i
c   s h e e t   u s e d   i f   1 13  
  o f   s h e e t   a c t u a l l y   u s e d
  w a s   w a s t e d   i n   m a k i n g
  tan k   ( T a k e     π = 3 14   )
10   A   l o n g   a   h i g h w a y   50
c o n i c a l   p i l l a r s   a r e   c o n s t r
u c t e d   E a c h   P i l l a r   h a s   b a
s e   d i a m e t e r   28   c m   a n d  
v e r t i c a l   h e i g h t     18 c m   f i
n d   t h e   t o t a l   cos t   o f   p
a n t i n g   t h e s e   p i l l a r s   a t  
t h e   r a t e   o f   R s   120   p e r
  m 2 ( T a k e   π =   22 7   )

Ashutosh Verma · Accepted Answer

Dear Student,

The solution to your ( 10th) query has been provided
below:

Given : 50 conical pillars with base diameter = 28 cm and vertical
height = 18 cm

So,

Radius of a conical pillar = r = 14 cm and Height of a
conical pillar = h = 18 cm

We know curved surface area of cone =
π r r2 + h2 , So

Curved surface area of a conical pillar =
227 × 14× 142 + 182 = 22 × 2× 196 + 324= 22 × 2× 520 =  22 × 2×22
8035 = 1003 354 cm2

So,

Curved surface area of 50 conical pillar = 50 × 1003 354 =
50167 7 cm2 = ( 50167 7 × 0 0001 ) m2 =
5 01677m2 ( We know 1 cm2 =
0 0001 m2 )

Also given : Rate of painting = 120 per m2 ,

Therefore,

Cost of painting these pillars = 120 × 5 01677 = 602
0124 ≈ Rs 602 ( Ans )

Hope this information will clear your doubts about topic

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