Measurement error is the positive difference between a measured amount and the actual amount.

For example, Diego measures a line segment as 5.30 cm. The actual length is 5.32 cm. The measurement error is 0.02 cm, because \(5.32-5.30=0.02\).

A percent decrease tells how much a quantity went down. It is written as a percentage of the starting amount.

For example, a store had 64 hats on Friday. It had 48 hats left on Saturday. The number of hats went down by 16.

This was a 25% decrease, because 16 is 25% of 64.

Percent error is a way to describe error as a percentage of the actual amount.

For example, a box is supposed to have 150 folders. Clare counts only 147 folders in the box. This is an error of 3 folders. The percent error is 2%, because 3 is 2% of 150.

A percent increase tells how much a quantity went up. It is written as a percentage of the starting amount.

For example, Elena had \$50 in the bank on Monday. She had \$56 on Tuesday. The amount went up by \$6.

This was a 12% increase, because 6 is 12% of 50. 

A repeating decimal has digits that keep going in the same pattern over and over. The repeating digits are marked with a line above them.

• The decimal representation for \(\frac13\) is \(0.\overline{3}\), which means 0.3333333 . . . .
• The decimal representation for \(\frac{25}{22}\) is \(1.1\overline{36}\), which means 1.136363636 . . . .