Calculate the Space Diagonal: Finding the Corner-to-Corner Distance in a 10cm Cube

Question

Shown below is a cube with edges equal to 10 cm.

What is the length of the inner diagonal of the cube?

101010

Video Solution

Solution Steps

00:00 Find the internal diagonal in the cube
00:04 We'll use the Pythagorean theorem in triangle DD'C
00:14 We'll substitute appropriate values and solve to find the diagonal
00:35 This is the diagonal in triangle DD'C
00:42 We'll use the Pythagorean theorem in triangle D'A'C
00:48 We'll substitute appropriate values and solve to find the diagonal
01:14 And this is the solution to the question

Step-by-Step Solution

To find the inner diagonal of a cube where each edge is 10 cm long, we will use the Pythagorean theorem in three dimensions. For a cube with edge length a a , the formula to find the diagonal d d is:

d=a3 d = a \sqrt{3}

In this problem, the edge length a=10 a = 10 cm. Substituting into the formula gives:

d=103 d = 10 \sqrt{3}

Calculating 103 10 \sqrt{3} , we estimate 31.732 \sqrt{3} \approx 1.732 . Thus:

d10×1.732=17.32 d \approx 10 \times 1.732 = 17.32

Rounded to one decimal place (as often required for physical measures), the length of the inner diagonal of the cube is approximately 17.3 17.3 cm.

Therefore, the correct choice is the one that matches this calculation, which is:

17.3 17.3 cm.

Answer

17.3 17.3 cm