For the ruler with a length of 9cm, three scale lines are determined on the ruler, so that the ruler can measure all the whole cm line segments from 1 to 9cm at one time. Three schemes are designed

For the ruler with a length of 9cm, three scale lines are determined on the ruler, so that the ruler can measure all the whole cm line segments from 1 to 9cm at one time. Three schemes are designed

2cm, 5cm, 7cm

Xiao Fang measures the length of a book with a ruler whose minimum scale unit is centigrade. Her result is 25.9 cm, of which
A: 2 is accurate, 5 and 9 are estimated, B: 2 and 5 are accurate, 9 is estimated
C: 2,5,9 are accurate, 2,5,9 are estimated D: 1

B: Two and five are accurate, nine is estimated
The key is that the minimum scale of that ruler is centimeter, and 9 in 25.9 is millimeter, so it must be estimated!

A ruler, most of the scale has been unable to see clearly, can see clearly scale has 5, with this ruler can directly measure how many different lengths

1-0 = 1 5-0 = 5 11-0 = 11 20-0 = 205-1 = 4 11-1 = 10 20-1 = 19 11-5 = 6 20-5 = 1520-11 = 94 + 3 + 2 + 1 = 10