waecE-LEARNING
Further Mathematics Paper 2, Nov/Dec. 2014  
Questions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Main
General Comments
Weakness/Remedies
Strength








Question 3

The volume of a sphere is increased by 6%. Calculate the corresponding percentage increase in its area.

 

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Observation

This question was reported to be quite unpopular among the candidates.  Majority of those who attempted it were also reported to have performed poorly.  Candidates were expected to recall that
. If volume of sphere = V = r3,  = 4pr2. Hence, dV = 4pr2dr.  =  = .
But  = 6%. This implies that  = 6 i.e  =  = 2%.
Surface area of a sphere = A = 4pr2.  = 8pr. Therefore, dA = 8prdr.  =  = .  Hence,  =  = 2 ´ 2 = 4%. i.e. The area is increasing by 4%.

 

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