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A hemispherical punch bowl of internal radius 9 cm is full to the brim with fruit punch. This liquid is transferred into small cylindrical bottles with diameter 3 cm and height 4cm. How many bottles can be filled before the punchbowl is empty?
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nice one Prasoon.
Brilliant :P
V. of hemisphere=2/3 22/7 9 9 9 (i) V.of cylinder=22/7 3/2 3/2*4 (ii)
(i)/(ii)
=1527/28=54 bottles (ANS.)
the volume of the liquid in the hemispherical bowl remains same when it is transfered to the cylindrical bottles. therefore,
volume of liquid in the bowl = total volume of liquid in the cylinders
3 2 ∗ π ∗ 9 ∗ 9 ∗ 9 = n π ∗ 2 3 ∗ 2 3 ∗ 4 , where n is the number of cylinders .
hence, n = 5 4
1/2.V ball = k.V bottle ---> 2/3 . phi . r ball^3 = k . phi . r bottle^2 . t_bottle ---> 2/3 . 9^3 = k . (3/2)^2 . 4 ---> 2 . 3 . 9^2 = k . 3^2 ---> k = 54. So, bottles will be needed to empty the bowl are 54. Answer : 54
To find the number of bottles needed to empty the bowl, we need to find the ratio of the volume of the bowl to the volume of each bottle. The volume of a sphere of radius r is given by 3 4 π r 3 and the volume of a right cylinder is given by π r 2 h , where r is the radius of the base and h is the height of the cylinder.
π ( 2 3 ) 2 4 3 2 π r 3 = 5 4
And pardon me, r = 9 and I did not mention that in the numerator of the ratio. Oops. :D
Volume of bowl = (2/3pi x 9 x 9 x 9) = 486pi
Volume of one bottle = (pi x 3/2 x 3/2 x 4) = 9pi
No. of bottles = (486pi/9pi) = 54
ncert question
This question is present in BMA IIT Foundation and Olympiad Explorer for class 9.
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Since the liquid just goes from one container to other containers, the total volume of the liquid remains the same.
Let n be the required no. of cylindrical bottles.
Volume of total liquid in hemispherical bowl = 3 2 π r 3 = 3 2 π ( 9 ) 3 c m 3
Volume of liquid in one bottle = π r 2 h = π ( 2 3 ) 2 × 4 c m 3
We have, 3 2 π ( 9 ) 3 = n π ( 2 3 ) 2 × 4
⟹ 3 2 × 7 2 9 = n ( 4 9 ) × 4
⟹ 2 × 2 4 3 = 9 n ⟹ n = 5 4
So, no. of bottles required = n = 5 4