In this week, I figured out an important question:

Now we know that in this cuboid, Height equals c, Width equals b, and Length equals a. We should give a equation to express d.

How to figure out the equation?

First, add a new line. We named it “e”

Second, use the Pythagorean theorem.so

Because a^2 + b^2= c^2

So e^2=a^2+b^2, and d^2=c^2+e^2

So d^2=a^2 + b^2 + c^2

at last, use radical sing to calculate a precise number of d.

I learned how to use and read number on micrometer. I think how to read is more important than use.

If you are facing to a number like the picture above, you should pay attention to the number above the number line of sleeve. In this picture, we just can see “4”, so write it down. Then we look at the number under the number line, we got 3 more hundredths, so it is (3*0.25). At last, the number of thimble is “8”, thousandths of an inch given by thimble, so we got”0.08″. At last is compute, 4+(3*0.25)+0.08=4.83