# Question: 3-D Diagonal

## Comment on 3-D Diagonal

### Why did you assume that there

Why did you assume that there's a right angle there? Are we meant to assume that if it isn't stated ### We're told that we have a

We're told that we have a RECTANGULAR box. So, there are 90-degree angles at each corner.

Cheers,
Brent

### does this formula work for a

does this formula work for a cube? I would assume so because all squares are rectangles but not vice versa--and thus the same for the 3D form of the figures. However, the answer in the example given here ( https://greprepclub.com/forum/tricky-each-edge-of-the-above-cube-has-length-1-if-an-ant-9679.html ) says that the L W and H of a cube are 1, but the total distance between opposite points on the figure is sqrt(5). This, however, does not comply with the formula above. Can you please provide some clarity? ### Yes, the formula in the video

Yes, the formula in the video will work for cubes as well.

NOTE: The formula finds the straight line distance (the shortest distance) between the opposite vertices.
That is, if a fly were to DIRECTLY travel from one vertex to the opposite vertex, we can use the formula to find that distance.

The question at https://greprepclub.com/forum/tricky-each-edge-of-the-above-cube-has-len... is slightly different.

In that linked question, the ant doesn't travel the shortest distance from A to B. Instead, the ant walks from point A to point B along the OUTSIDE of the cube.

Does that help?

Cheers,
Brent