To square a footing for a foundation could I use 18-24-30 to get a 90-degree angle?

Question

Using the 3-4-5 method if I measured out 18 feet on one side of the angle and 24 feet on the other angle, if the 3rd side equals to 30 will the corner be square? all three numbers being a multiple of 6. I kinda understand using smaller numbers like 12, 3x4=12 and 16, 4x4 =16 and 20 5x4=20 but I'm confused when using larger numbers. This builder use 26, 28, 35 how does that work. the corner I'm trying to measure is 26'10" by 30'10 " a little bit bigger than the acual foundation.

Answer 1

Yes. 18-24-30 is a 3-4-5 triangle, and measuring out 18 and 24, then measuring the cross line (hypoteneuse) at 30 will get you a right angle.

I'm not sure about 26,28,35. *21*, 28, 35 is a 3-4-5. Maybe he did a typographical error (26 instead of 21).

.

Answer 2

You are correct to use "scaled" versions of the 3-4-5 right triangle. there is also the 5-12-13 and 8-15-17 that are lesser known... I'd use your 18-24-30 that youre comfortable with. Just measure 18 and 24 on either the 26.833 or 30.8333 sides (10 inches is .8333 feet) and if they are exactly 30 ft then you have right angle....

You builder is probably not using 26-28-35 since this not a right angle....

Too be really accurate the cross distance of 26.8333 and 30.8333 should be 40.8744 feet which is close enough to 40 feet 10.5 inches...

Answer 3

it rather is a sturdy element. My wager is that as quickly as you hang your foot off of something, (which comprise a chair), it of course makes a one hundred twenty degree perspective. It in basic terms makes a ninety degree perspective while your bodyweight on good of it forces it to.

Answer 4

The first one works the second one doesn't. If you are going to work in feet and inches, I would convert all dimensions to inches to make it simpler.