Ravi can do a piece of work in 30 days while Prakash can do it in 40 days. In how many days will they finish it together?
Options:
(A) 17 1/7 days
(B) 27 1/7 days
(C) 23 2/7 days
(D) 16 4/11 days
(E) none of these
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1/30 + 1/40 = 7/120
120/7 = 17 1/7 days So the answer is: (A).
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A man rows his boat 75 km downstream and 45 km upstream, taking 2 1/2 hours each time. Find the speed of the stream?
Options:
(A) 5 kmph
(B) 6 kmph
(C) 9 kmph
(D) 8 kmph
(E) 1 kmph
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Speed downstream = d/t = 75/(2 1/2) = 30 kmph
Speed upstream = d/t = 45/(2 1/2) = 18 kmph
The speed of the stream = (30 - 18)/2 = 6 kmph So the answer is: (B).
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The radius of a cone is 4 m, height 5 m. Find the curved surface area?
Options:
(A) 1
(B) 3
(C) 5
(D) 7
(E) 9
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Cone curved surface area = rl = 22/7 4 5 = 440/7 = 62 6/7
Slant height (l) = r(power2)+h(power2) = 16+9 = 25 = 5 So the answer is: (C).
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