This is the concept of areas of solid materials; the surface area of the cylinder whose radius is 2.5 cm and lateral area is 20 pi cm^2 will be: Surface area of cylinder is given by:
SA=(area of cyclic sides)+(lateral area)
SA=2πr^2+πrl
Area of the cyclic sides will be:
Area=2πr^2
=2*π*2.5^2
=12.5π cm^2
The lateral area is given by:
Area=20π cm^2
Therefore the surface area of cylinder will be:
SA=(12.5π+20π) cm^2
SA=32.5π cm^2
The answer is 32.5π cm^2
Well this is simple a calculator type problem...but if you are curious as the the algorithm used by simple calculators and such...
They use a Newtonian approximation until it surpasses the precision level of the calculator or computer program..
A newtonian approximation is an interative process that gets closer and closer to the actual answer to any mathematical problem...it is of the form:
x-(f(x)/(df/dx))
In a square root problem you wish to know:
x=√n where x is the root and n is the number
x^2=n
x^2-n=0
So f(x)=x^2-n and df/dx=2x so using the definition of the newton approximation you have:
x-((x^2-n)/(2x)) which simplifies further to:
(2x^2-x^2+n)/(2x)
(x^2+n)/(2x), where you can choose any starting value of x that you desire (though convergence to an exact (if possible) solution will be swifter the closer xi is to the actual value x)
In this case the number, n=95.54, so a decent starting value for x would be 10.
Using this initial x in (x^2+95.54)/(2x) will result in the following iterative sequence of x.
10, 9.777, 9.774457, 9.7744565, 9.7744565066299210578124802523397
The calculator result for my calc is: 9.7744565066299210578124802523381
So you see how accurate the newton method is in just a few iterations. :P
Risk - 5 = 16. It is just mathematical language.
If the volume of a cylinder is x, then the volume of a cone with same height and diameter is x/3
so
if the cone is 72ft³ then the cone with same base and height is 72/3ft³=24ft³
answer is A
