A similar math problem in grade three! !

There is no A5B5 in the picture, but there is A5B5 in the question? ?

Because the triangle a4b4o is similar to a 1b 1o, so? ob4/ob 1 = a4 B4/a 1b 1 = 20/80 = 1/4( 1)

Because? ob 1 = ob4+B4 B3+B3 B2+B2 b 1，b4b3=b3b2=b2b 1。

So what? Ob 1 = ob4+3b2b1substitution (1)? Ob4/(ob4+3bb2b1) =1/4, that is? ob4=b2b 1

Because the triangle a4b4o is similar to a3b3o, a3b3/a4b4=(ob4+b3b4)/ob4=2(2).

A4b4 is known to be equal to 20. Substitution into (2) gives a3b3=40.

Similarly, the triangle a4b4o is similar to a2b2o, so A2B2/A4B4 = (OB4+B4 B3+B3 B2)/OB4 = 3 (3).

It is known that a4b4 is equal to 20. If it is substituted into (3), a2b2=60.

A: a2b2 is 60 meters long and a3b3 is 40 meters long.