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15 Dec 2018, 10:17
Kudos
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A
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Difficulty:
85%
(hard)
Question Stats:
47% (02:06) correct
53%
(01:55)
wrong
based on 128
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Sphere.jpg [ 10.88 KiB | Viewed 7011 times ]
A spherical ball was cut into eight equal pieces along the same axis (as shown in figure). The total surface area of the eight pieces is how much more, in square units, than the original surface area of the spherical ball? [ The surface area of the sphere = 4ΠR2]
(1) The diameter of the spherical ball = 10 units.
(2) The total surface area of eight halves is 3 times that of the original surface area.
16 Dec 2018, 05:05
Kudos
Bookmarks
Given : A spherical ball was cut into eight equal pieces along the same axis (as shown in figure).
DI Question : The total surface area of the eight pieces is how much more, in square units, than the original surface area of the spherical ball? [ The surface area of the sphere = 4ΠR2]
So, total surface area of one piece = 1/8*(4ΠR^2) + 1/2 ΠR^2 + 1/2 ΠR^2 = 3/2 ΠR^2
Total surface area of 8 pieces = 8 * 3/2 ΠR^2 = 12 ΠR^2
So, total surface area of the eight pieces is more, in square units, than the original surface area of the spherical ball by 12 ΠR^2 - 4 ΠR^2 = 8 ΠR^2.
Statement (1) : The diameter of the spherical ball = 10 units.
Since Diameter is given, hence radius is known. So we can calculate the value.
SUFFICIENT
Statement (2) : The total surface area of eight halves is 3 times that of the original surface area.
This doesn't add any extra information and hence we can't calculate the value.
SUFFICIENT
Answer A
DI Question : The total surface area of the eight pieces is how much more, in square units, than the original surface area of the spherical ball? [ The surface area of the sphere = 4ΠR2]
So, total surface area of one piece = 1/8*(4ΠR^2) + 1/2 ΠR^2 + 1/2 ΠR^2 = 3/2 ΠR^2
Total surface area of 8 pieces = 8 * 3/2 ΠR^2 = 12 ΠR^2
So, total surface area of the eight pieces is more, in square units, than the original surface area of the spherical ball by 12 ΠR^2 - 4 ΠR^2 = 8 ΠR^2.
Statement (1) : The diameter of the spherical ball = 10 units.
Since Diameter is given, hence radius is known. So we can calculate the value.
SUFFICIENT
Statement (2) : The total surface area of eight halves is 3 times that of the original surface area.
This doesn't add any extra information and hence we can't calculate the value.
SUFFICIENT
Answer A
16 Dec 2018, 23:06
Kudos
Bookmarks
ans is A
Total surface area of each piece= 4πr^2/8 + πr^2
So total surface area of eight pieces = 4πr^2+8 πr^2
difference= 8 πr^2
Statement 1 gives r which is sufficient.
Total surface area of each piece= 4πr^2/8 + πr^2
So total surface area of eight pieces = 4πr^2+8 πr^2
difference= 8 πr^2
Statement 1 gives r which is sufficient.
