3. First find out the sum of the land area of these European countries in the table below, and then compare it with our country's land area. What have you found?
Teacher! This is simple! 245000+551600+357000+43000+301300+505900=2003800 square kilometers, my country's land area is about 9600000 square kilometers, 96000002003800, so my country's land area is larger than the land area of these European countries.
is indeed simple, but many students have done it wrong, and some students even made mistakes five or six times!
Why? One word - lazy !
first did not write vertical style, but just oral calculation. The oral calculation of such a large 6 numbers was wrong after calculating. He also asked the teacher, "Where am I wrong?"
forced her to write vertical style, but the vertical style was written crookedly (digits are not aligned), and of course it was wrong again!
forced her to draw a dotted line again, so that the numbers are aligned, and finally they are closer to the correct answer! But it's still wrong! Adding 6 numbers one piece is too big, of course it is easy to make mistakes!
finally forced her to add two numbers and two numbers slowly, and it was finally right!
is so tired! Finally right! This student smiled happily! (But I want to cry! If you really don’t know how to do it, the teacher will teach you slowly; but you are always lazy and make some lowest-level calculation errors, is it interesting?)
I said: If you are not lazy and align digitally at the beginning, and add two numbers in vertical form, how could you waste so much time?
She glanced at me blankly and left!
! I guess next time she does a similar question, she will be lazy and make mistakes many times!
Finally, I comforted myself: Not bad, at least she didn’t copy other people’s answers like some lazy students!
4. Calculate the area of the shadowed part in the figure below.
You can take a look at it yourself. Isn’t the sum of the areas of the two squares minus the sum of the two blank triangles the area of the shadow part? Many students know this, but they just don’t know how to do it.
marks all the data on the graph, which is actually easy to calculate!
The area of a large square: 8×8=64 square centimeters .
The area of a small square: 6×6=36 square centimeters.
The area of the blank triangle on the left: 8×8÷2=32 square centimeters.
The area of the blank triangle to the right: (8+6) × 6÷2=42 square centimeters.
The area of the shadowed part = 64+36-(32+42) = 26 square centimeters.
