Readings

A ruler's reading is to 0.1 cm
A vernier calipers's reading is up to 0.01cm
A micrometer's reading is also up to 0.01cm

On the vernier calipers, the reading on the top will be called the main scale, while the one at the bottom will be called vernier scale.
When we count the reading on the main scale,we will round it off to 1 decimal point.When we count the reading on the vernier scale,we round it off to 2 decimal points.

On the micrometer,the left is called sleeve while the right is called thimble.

When there's an X positive zero error, we minus X from the observed reading and vice versa.

Measurements
micro = 1 millionth
milli = 1 thousandth
centi = 1 hundredth
deci = 1 tenth
kilo = 1 thousand
mega = 1 million

1cm = 10 mm
1m = 1oocm
1 km to the power of 3 = 1000 000 000 m to the power of three
1 cm to the power of 3 = o.ooooo1m to the power of 3
1mm to the power of 3 = 0.000000001 m to the power of 3

Volume of a cube = L to the power of 3
Volume of a rectangular block = L x B x H
Volume of a sphere = 4
---- pie x radius x radius
Volume of a cylinder = pie x radius x radius x height