Page 165 - NUMINO Challenge_D1

Answer
Key

3 (Length of the rope) (Vertical length of the Creative Thinking p.118~p.119

fence) (Radius of the yellow part)

1 , 2 m 1 Turn the smaller square, as shown below.
4

4 (5 5 3.14) 3 (1 1 3.14) 1
4 4

1 10 cm
4
(2 2 3.14) 62.8 m2

5 5 3.14 10 10 1 78.5 50 28.5 cm2
2
Problem solving

1 120 2 They all arrive at the same time. Let represent

60 6 m the diameter of the big circle. If you divide in

120 three parts, it becomes . Since ,
60
1 1 3.14 1 60 and are the diameters of each small circle,

3 5m 300 the length of the path becomes

5 3.14 1 3.14 1 3.14 1
6 6 3.14 6 2 2 2

3.14 1 , which is equal to
2

6 6 3.14 5 1 1 3.14 2 94.2 2.09 the value of 3.14 1 . The result is the
6 3 2

96.29 same when you divide in several parts.

96.3 m2

2 3

4 cm 2 cm 120 120 120 120 120 120

4 2 8 cm2 3.14 cm2
2 2 3.14 1
In the picture, the length of the path of is
4 twice the length of the perimeter of a circle with
10cm radius. Therefore, the total distance Point
(8 4) (3.14 4) 32 12.56 44.56cm2
moves is 20 3.14 2 125.6 cm.

4 Note that Coin itself is rotating while it makes

a revolution around Coin . Divide the distance

that the center of Coin moves by the

circumference of Coin to find the number of

rotations that the center of Coin makes during

one complete revolution around Coin . When

the diameter of the Coin is , the distance Coin

moves is (2 ) 3.14 2 ( 3.14). The

perimeter of Coin is ( 3.14).

Therefore, Coin rotates 2 ( 3.14) 2 times.
( 3.14)

NUMINO Challenge D1