a well is 7.2 m deep . the cost of cementing its inner surface at 75 paisa per decimetre sq. is ₹ 11880.determine the radius of the well
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Find the volume
Volume ×cost =total cost
Volume ×cost =total cost
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Solution :-
Let r be the radius of the well.
Now,
Height = 7.2 m or 72 decimeter
Area cemented for Rs. 0.75 = 1 dm²
Area cemented for Rs. 11880 = 1*11880/0.75
= 11880/0.75
Curved Surface Area of the well = 15840 sq dm
Curved Surface Area of cylinder = 2πrh
15840 = 2*22/7*r*72
r = (15840*7)/3168
r = 110880/3168
r = 35 dm
So, Radius of the well is 35 decimeter or 3.5 m
Answer.
Let r be the radius of the well.
Now,
Height = 7.2 m or 72 decimeter
Area cemented for Rs. 0.75 = 1 dm²
Area cemented for Rs. 11880 = 1*11880/0.75
= 11880/0.75
Curved Surface Area of the well = 15840 sq dm
Curved Surface Area of cylinder = 2πrh
15840 = 2*22/7*r*72
r = (15840*7)/3168
r = 110880/3168
r = 35 dm
So, Radius of the well is 35 decimeter or 3.5 m
Answer.
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