Room 3

Scoil Chrónáin

St Cronan's Senior National School, Swords

Room 3

5/21/2015

The third room:Skippy and Anna have the second key number. They have gone through the second locked door. Here there is a diagram.

There are two overlapping circles inside a rectangle. The rectangle is the second key number of centimetres long and 5 centimetres high.
How far apart are the centres of the two circles?
Square this answer and subtract one. This will give you the third key number.

Here are some diagrams with our solutions:

2 Comments

Charlé

5/20/2015 07:22:38 pm

1. The diameter of each circle is 5 so the radius is 2.5.
2. This is the same on both circles.
3. Add the two outside radius, from the middle, to the outside edges of the square. 2.5 + 2.5 = 5.
4. The total length is 9 so the middle bit is 9-5 = 4.
5. 4 squared is 16 and 16 - 1 = 15 so the key to the third door is 15.

Lucy

5/20/2015 07:26:06 pm

First I got 2.5 as the radius of the circle and added this together for the edges of the two circles to get 5. 4 + 5 = 9 so if the outside radius was five the length in the center was 9-5 = 4.
Therefore the key is 15 because 4 squared = 16 - 1 = 15

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