Question 1196938
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The 4 by 10 rectangle has a line down the middle to make two identical 4 by 5 rectangles.


The original 4 by 10 rectangle has area of 4*10 = 40 square cm


The smaller rectangles have area of 4*5 = 20 square cm each, so that doubles to 2*20 = 40 square cm.


We can either say:
4*10 = 40
or
2*(4*5) = 2*20 = 40
or
4*5 + 4*5 = 20+20 = 40


What you posted of 4x5+4x5 and (4x5)x2 are both correct. This is of course assuming the x refers to multiplication (and not a variable). I used the asterisk symbol * to represent multiplication in the work shown above.
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