24050

Solution to challenge 3:
The diameter of each circle was 5 centimetres. We used the key number (9) to find out how big the overlap was. We did this by taking out the overlap and the length of the two circles next to each other was ten centimetres. We then subtracted the key number from the diameter of both circles to get the size of the overlap which was one centimeter. We used our results from this to find out how far apart the centers were. We knew that 2.5 centimetres is radius of each circle. Then we added another 2.5 centimetres to get the distance between the centers of the two circles which was equal to five centimetres. Then we subtracted the length of the overlap from the distance between the centers of the two circles which was 4 centimetres. Then we squared 4 which was 16 and then subtracted 1 to get the third key number. The answer was 15.