Your friend and your cousin discuss measuring with a ruler. Your friend says that you must always line up objects at the zero on a ruler. Your cousin says it does not matter. Decide who is correct and explain your reasoning.

Your friend is correct.

Step-by-step explanation:

It is given that your friend says that you must always line up objects at the zero on a ruler. Your cousin says it does not matter.

We need to decide who is correct.

When we measure the length of any object we have to line up objects at the zero on a ruler, so that mark on the rules along the other end of the object represents the length of the object.

Let we have a pencil of length 5 cm.

If we place the rules on 0, then 5 is the mark on the rules along the other end of the pencil. So, height  of the pencil is 5 cm.

If we place the rules on 1, then 6 is the mark on the rules along the other end of the pencil. So, height  of the pencil is 6 cm, which is not correct.

Therefore, your friend is correct.