Question 349269
Extend a line from the top of the block to the vertical line thru the center of the pipe.
You get a right triangle with r as the hypotenuse.
{{{r^2 = (5-r)^2 + (r-1)^2}}}
If you solve that you'll get 6 ± sqrt(10)
6 - sqrt(10) is the answer.
6 + sqrt(10) puts the block on the other side of the pipe, between the pipe and the wall.
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btw, that's not a "large" pipe, less than 3 ft OD.