The figure above represents a right circular cylindrical tube made out

Question

https://gmatclub.com/forum/download/file.php?id=39079 The figure above represents a right circular cylindrical tube made out of paper. The circumference of each circular base is 10 centimeters, the length of AB is 12 centimeters, and BD is a diameter of a base. If the tube is cut along AB, opened and flattened, what is the length of AD in centimeters? (A) 13 (B) 17 (C) 22 (D) 2√61 (E) √146.5 2017-12-08_1440_002.png

Luckisnoexcuse · Answer

Radius = >
2*pie * r = 10
r = 5/pie
ABD will be right angle Triangle 
AD is Hypotenuse and hence can be calculated
AD =  \sqrt{(12^2 + (5/pie)^2)} 
AD =  \sqrt{(144 + 25/~9.5)} = \sqrt{146.5} 
E

exc4libur · Answer

If the tube is opened and flattened, then we have a rectangle with length 12 = AB, and width 10 = the circumference.

Now, lines BD and AC are equal to half the width = 10/2 = 5.

So to find the distance AD, we need to find the diagonal of the rectangle with length 12 = AB and width 5 = BD

a^2+b^2=c^2, 12^2+5^2=c^2, 169=c^2, c=13

(A) is the answer.

KarishmaB · Answer

When you cut along AB and open it, you get a rectangle. Notice that in this rectangle, A is on the corner and D is in the centre of the opposite edge. So ABD will form a right triangle.

AB^2 + BD^2 = AD^2

AB is simply the length of the tube at 12 cm but notice what BD is. It is half the circumference of the circular base (since it is opened and flattened) which is 10 cm. So BD = 10/2 = 5 cm

This will be a 5-12-13 triangle then and AD will be 13 cm.

Answer (A)

KarishmaB · Answer

Responding to a pm: Here is the original roll. Rectangular Roll Original.jpg When you open it, this is what it looks like. Rectangular Roll.jpg

MSarmah · Answer

Got the answer to be A

Can anyone explain how it is D??

Bunuel · Answer

The correct answer is A. Edited. Thank you.

MSarmah · Answer

Welcome Brunnel

bumpbot · Answer

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The figure above represents a right circular cylindrical tube made out

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