# Lesson 9

Measurement Error

Let’s use percentages to describe how accurately we can measure.

### Problem 1

The depth of a lake is 15.8 m.

- Jada accurately measured the depth of the lake to the nearest meter. What measurement did Jada get?
- By how many meters does the measured depth differ from the actual depth?
- Express the measurement error as a percentage of the actual depth.

### Problem 2

A watermelon weighs 8,475 grams. A scale measured the weight with an error of 12% under the actual weight. What was the measured weight?

### Problem 3

Noah's oven thermometer gives a reading that is 2% greater than the actual temperature.

- If the actual temperature is \(325^\circ\text{F}\), what will the thermometer reading be?
- If the thermometer reading is \(76^\circ\text{F}\), what is the actual temperature?

### Problem 4

At the beginning of the month, there were 80 ounces of peanut butter in the pantry. Now, there is \(\frac13\) less than that. How many ounces of peanut butter are in the pantry now?

A:

\(\frac23 \boldcdot 80\)

B:

\(\frac13 \boldcdot 80\)

C:

\(80-\frac13\)

D:

(From Unit 6, Lesson 1.)
\(\left(1+\frac13\right)\boldcdot 80\)

### Problem 5

- Fill in the table for side length and area of different squares.
side length (cm) area (cm ^{2})3 100 25 \(s\) - Is the relationship between the side length of a square and the area of a square proportional?