Reading a ruler well

A ruler can be broken at one end. Its start may be missing. So its first mark may not be 0.

A reading is the number at a mark. The near end is where the object starts. The far end is where it stops.

Rule: Length = far-end reading − near-end reading.

Example: a ribbon starts at 2 cm and ends at 15 cm. The near-end reading is 2 cm. The far-end reading is 15 cm. The ribbon's length is 15 − 2 = 13 cm.

Between two cm numbers, a reading has a dot, like 5.4 cm. Each cm has 10 small marks. 5.4 cm is 5 cm and 4 small marks more.

Look straight down at each mark. From the side, the reading looks different.