Question

report the following measurement to the correct number of significant figures.
(image of a ruler with a green bar, and multiple - choice options: 7.200 cm, 7.20 cm, 7.2 cm, 7 cm)

Explanation:

Step1: Analyze the ruler's scale

The ruler has markings where each major division (like between 6 and 7, 7 and 8) is 1 cm, and each major division is divided into 10 smaller divisions. So the smallest division (precision) is \( \frac{1\ cm}{10} = 0.1\ cm \).

Step2: Determine the measurement

The object's length is measured from the start (let's assume the left end is at 0, but here the visible part starts around 6, but the key is the end at 7.2 cm? Wait, no, looking at the ruler, the green bar ends at a position. Wait, the ruler has 6, 7, 8 marked. The distance between 6 and 7 is 1 cm, divided into 10 parts, so each part is 0.1 cm. The green bar's end is at 7.2 cm? Wait, no, let's see: the left end is at 6? No, the left end of the green bar is at the left edge, but the ruler starts with 6. Wait, the green bar's right end is at 7.2 cm? Wait, the ruler's scale: from 6 to 7 is 1 cm, 10 divisions, so each division is 0.1 cm. The green bar's length: let's say the left end is at 6.0 cm (assuming the left edge is at 6.0), and the right end is at 7.2 cm. So the length is 7.2 - 6.0 = 1.2? No, wait, maybe the left end is at 0, but the ruler is marked from 6. Wait, no, the problem is to report the measurement. The key is significant figures: when measuring with a ruler, the number of significant figures is determined by the precision. The ruler here has a precision of 0.1 cm (since 1 cm is divided into 10 parts). So the measurement should be reported to the tenths place. Let's check the options: 7.2 cm has two significant figures, and the precision is 0.1 cm, so we can report to one decimal place (tenths), which is two significant figures. Wait, the options: 7.2 cm is correct because the ruler's precision is 0.1 cm, so we can measure to the tenths place. Let's confirm: the smallest division is 0.1 cm, so the measurement is 7.2 cm (the right end is at 7.2 cm, assuming the left end is at 0, but maybe the left end is at 6.0, so 7.2 - 6.0 = 1.2? No, maybe the ruler is showing the length from 0 to 7.2? Wait, the image shows the green bar with the ruler marked 6,7,8. So the length of the green bar: let's say the left end is at 6.0 cm (the first mark after 6 is 6.1, etc.), and the right end is at 7.2 cm. So the length is 7.2 - 6.0 = 1.2? No, that can't be. Wait, maybe the ruler is measuring the length from the left (where the green bar starts) to the right (where it ends). Wait, maybe the green bar's length is 7.2 cm? No, the options are 7.200, 7.20, 7.2, 7. The correct one is 7.2 cm because the ruler's precision is 0.1 cm, so we can report to the tenths place, giving two significant figures. The option 7.2 cm is correct.

Answer:

7.2 cm (Option: 7.2 cm)