Page 111 - NUMINO Challenge_A2

Answer
Key

Type Study An Old Ruler

1 The sum of the lengths between every 2 marks is equal to the difference between the
marks on each end of the ruler.

2 cm 3 cm 1 cm 2 cm

2 Find the lengths that can be measured between every 2 marks.

Number of How the Lengths Can Be Measured Measurable Length
Different
Lengths 2 cm 3 cm 1 cm 2 cm 1 cm, 2 cm, 3 cm
2 cm 3 cm 1 cm 3 cm, 4 cm, 5 cm
One
Two 2 cm 4 cm 1 cm 2 cm 6 cm
Three 3 cm 3 cm
2 cm
5 cm

3 cm 6 cm 2 cm
6 cm 1 cm

Four 2 cm 3 cm 1 cm 2 cm 8 cm
8 cm

3 Find all the measurable lengths in 2 .
The measurable lengths are: 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, and 8 cm.

Problem solving

1 Lengths that can be measured with one length of the ruler: 1 cm, 2 cm, 3 cm, and 4 cm

Lengths that can be measured with two lengths of the ruler: 1 4 5 cm, 2 3 5 cm
4 2 6 cm

Lengths that can be measured with three lengths of the ruler: 1 4 2 7 cm
4 2 3 9 cm

Lengths that can be measured with four lengths of the ruler: 1 4 2 3 10 cm
Therefore, the length that cannot be measured with the ruler is 8 cm.

6 NUMINO Challenge A2