Question

a .870 inches
b .970 inches
c 9.70 inches
d 8.71 inches

Explanation:

Step1: Analyze the dial caliper

The dial caliper has a main scale and a dial (vernier - like for the dial). The dial is marked with 0.001" per division. First, we look at the main scale (the linear part) and the dial reading. Wait, actually, for a dial caliper, the main scale gives the integer and decimal part, and the dial gives the thousandths. But looking at the options, the values are around less than 10 inches (except c which is 9.70 but the caliper's jaws are open, and the main scale seems to have markings that are likely in tenths or something, but let's check the dial. The dial shows a reading. Wait, the dial has a pointer. Let's see the main scale: the caliper's main scale, when we look at the position of the sliding part, but maybe a better way: the dial is marked with 0 - 100 (since 0,10,20,...90,0). The pointer is at 70 on the dial? Wait no, the dial has 0 at the top, 10,20,...90,0. Wait the needle is pointing at 70? Wait no, the numbers on the dial: 0,10,20,30,40,50,60,70,80,90,0. Wait the needle is at 70? Wait no, the label on the dial says 0.001", so each small division is 0.001". But maybe the main scale is in inches, and the dial is for thousandths. Wait, the options are a:.870, b:.970, c:9.70, d:8.71. Let's think about the caliper's range. The caliper's jaws are open, and the main scale markings: the left part has 0,1,2,... and the right part too. But the key is the dial reading. Wait, the dial's pointer: let's see, the dial has 0 at the top, and the needle is at 70? Wait no, the numbers on the dial: 0,10,20,30,40,50,60,70,80,90,0. Wait the needle is at 70? Wait, no, maybe I misread. Wait the dial has "0.001"" written, so the dial is for thousandths of an inch. Now, the main scale: if the main scale is showing, say, 0.8 inches (since the options are around 0.8 - 0.9 or 8 - 9 or 9 - 10). Wait, the option a is.870, which is 0.8 + 0.070. Wait, the dial: if the dial has 100 divisions (from 0 to 100, but marked as 0,10,...90,0), so each division is 0.001". So if the dial shows 70 divisions, that's 0.070". Then the main scale: if the main scale is at 0.8 inches (since the options are.870, which is 0.8 + 0.070). So 0.8 + 0.070 = 0.870, which is option a? Wait no, wait maybe the main scale is 0.9? Wait no, let's check the options. Option b is.970, which would be 0.9 + 0.070. But the dial: wait the needle is at 70? Wait the dial's numbers: 0,10,20,30,40,50,60,70,80,90,0. So from 0 to 10 is 0.010", so each 10 is 0.010", so each small division is 0.001". So if the needle is at 70, that's 0.070". Now, the main scale: the sliding part's main scale reading. Let's see, the main scale on the caliper: the left part has 0,1,2,... and the right part. Wait, the caliper's main scale: when the sliding part is at a position, the main scale's integer part? Wait, no, the caliper's main scale for inches: the standard dial caliper for inches, the main scale has 1 inch divided into 10 tenths, each tenth into 10 hundredths, so 0.1" per major division, 0.01" per minor? No, wait, a dial caliper for inches: the main scale (the bar) has markings where each inch is divided into 10 parts (0.1" each), and each 0.1" is divided into 10 parts (0.01" each). The dial is then for thousandths, with 100 divisions (0.001" each), so one full rotation of the dial is 0.1" (100 * 0.001"). So, to read the dial caliper: 1. Read the main scale: the value to the left of the zero on the sliding scale (the dial's carrier) in inches, to the nearest 0.01" (hundredth). 2. Read the dial: the number of divisions the needle has moved past zero, multiplied by 0.001" (thousandth). 3. Add them together. Now, looking at the image: the main scale (the bar) has markings. Let's assume that the main scale reading (the part before the dial) is 0.8" (since the options are.870,.970, etc.). Then the dial: the needle is at 70 divisions (since it's pointing at 70 on the dial). So dial reading is 70 * 0.001" = 0.070". Then total reading is 0.8" + 0.070" = 0.870", which is option a. Wait, but let's check the options again. Option a is.870 inches, option b is.970, option c is 9.70 (too big, since the caliper's jaws are not that long), option d is 8.71 (also too big). So the correct reading should be.870 inches, which is option a.

Step2: Verify the options

- Option a:.870 inches: matches the calculation (main scale ~0.8" + dial 0.070" = 0.870").
- Option b:.970 inches: would require main scale 0.9", but the main scale doesn't seem to be at 0.9" (the sliding part's zero is not at 0.9").
- Option c:9.70 inches: way too big, the caliper's length is not that long, and the jaws are open for a small measurement.
- Option d:8.71 inches: also too big, same reason as c.

Answer:

a. .870 inches