Mensuration

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Mensuration

by harsh.champ » Mon Feb 08, 2010 2:53 pm
A closed wooden box of thickness 0.5 cm and length 21 cm, width 11 cm, and height 6 cm, is painted on the inside. The cost of painting is Rs 70. What is the rate of painting in rupees per sq. cm?

(A)0.7
(B)0.5
(C)0.1
(D)0.2
(E)0.8

The OA is C.
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by ajith » Mon Feb 08, 2010 9:25 pm
harsh.champ wrote:A closed wooden box of thickness 0.5 cm and length 21 cm, width 11 cm, and height 6 cm, is painted on the inside. The cost of painting is Rs 70. What is the rate of painting in rupees per sq. cm?

(A)0.7
(B)0.5
(C)0.1
(D)0.2
(E)0.8

The OA is C.
the inside lengh will be 20 will be 10 and height would be 5
inside surface area = 2*10*20 + 2*10*5 +2*20*5 = 400+100+200 = 700 sqcm
700 sqcm costs 70 rupees hence 1 sqcm costs = 0.1 rupees
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by shashank.ism » Wed Feb 10, 2010 12:11 pm
harsh.champ wrote:A closed wooden box of thickness 0.5 cm and length 21 cm, width 11 cm, and height 6 cm, is painted on the inside. The cost of painting is Rs 70. What is the rate of painting in rupees per sq. cm?

(A)0.7
(B)0.5
(C)0.1
(D)0.2
(E)0.8

The OA is C.
thickness of box = 0.5 so dimension of box from inside = 20cm x 10cm x 5cm
cost of painting = surface areaxrate -->70 = (2*10*20 + 2*10*5 +2*20*5)xrate
--> rate=70/700 =0.1

Ans C
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