Math Is Fun Forum

adpqadpq

Member

Registered: 2017-02-03

Posts: 18

Geometry Help Please

To be able to walk to the center C of a circular fountain, a repair crew places a 16-foot plank from A to B and then a 10-foot plank from D to C, where D is the midpoint of Line AB . What is the area of the circular base of the fountain? Express your answer in terms of pi.

Help is greatly appreciated!

thickhead

Member

Registered: 2016-04-16

Posts: 1,086

Re: Geometry Help Please

You have to define what A and B are.

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{1}Vasudhaiva Kutumakam.{The whole Universe is a family.}
(2)Yatra naaryasthu poojyanthe Ramanthe tatra Devataha
{Gods rejoice at those places where ladies are respected.}

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Geometry Help Please

Hi adpqadpq;

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,626

Re: Geometry Help Please

hi adpqadpq

Welcome to the forum.

There's a difference here between the engineering problem where you actually want to get to the centre without getting your feet wet and the geometry problem where we assume that lines have zero 'thickness'.  The dotted lines on my diagram show that you'd have to overlap the second plank on the first in order to make a secure platform.  But I'll assume we meant to ignore that and take CD as 10 and the chord AB as 16.

It's a property of all circles that a line from the centre of the circle to the centre of any chord will be at right angles to the chord.  In other words angle ADC is 90.  So you can use Pythagoras theorem to calculate AC squared.  Don't bother to find the square root because you want radius squared for the area.  (pi r squared)

Hopefully that should be enough for you to complete the question.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

adpqadpq

Member

Registered: 2017-02-03

Posts: 18

Re: Geometry Help Please

I got the correct answer! Thanks bob bundy!