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If the radius of a sphere is increased by 50%, find the increase percent in the volume.
337.5%
325%
225%
237.5%
237.5%
Use the success multiplier method: since volume is proportional to r3, if r becomes 1.5 times, the new volume becomes (1.5)3=3.375 times the initial volume, representing a 337.5% increase.
Radius of a sphere is increased by 50%
V=34тАЛ╧Аr3
Use the success multiplier method: since volume is proportional to r3, if r becomes 1.5 times, the new volume becomes (1.5)3=3.375 times the initial volume, representing a 337.5% increase.
Many students calculate the new volume multiplier (3.375) and mistakenly choose 337.5% as the final value, forgetting that the question asks for the 'increase percent' in the volume (3.375VтИТV=2.375V=237.5%). Wait, let's verify: New Volume = 3.375V0тАЛ. Increase in Volume = 3.375V0тАЛтИТV0тАЛ=2.375V0тАЛ, which is 237.5%.
Step 1: Understand the formula for the volume of a sphere
The volume of a sphere depends on the cube of its radius: V=34тАЛ╧Аr3.
V=34тАЛ╧Аr3
Step 2: Determine the new radius after a 50% increase
If the radius is increased by 50%, the new radius becomes: rтА▓=r+0.50r=1.5r=23тАЛr
rтА▓=1.5r
Step 3: Calculate the new volume
Substitute the new radius into the volume formula: VтА▓=34тАЛ╧А(1.5r)3=34тАЛ╧А(3.375r3)=3.375V
VтА▓=3.375V
Step 4: Find the percentage increase in volume
The percentage increase is given by VVтА▓тИТVтАЛ├Ч100%. Since VтА▓=3.375V, the increase is: (3.375тИТ1)├Ч100%=2.375├Ч100%=237.5%
\text{Increase percent} = 237.5\
D is correct because when the radius is increased by 50%, the new volume becomes 3.375 times the original volume, resulting in an increase of 237.5% (2.375V).
For any 3D object, if linear dimensions scale by a factor k, surface area scales by k2 and volume scales by k3. Knowing this relation saves valuable time in competitive exams.