Question

Help please!!!!!!!I don’t know this! Tyy

Answer 1

Answer: Choice C.  4*sqrt(6)

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Explanation:

Each cube has a side length of 4. Placed together like this, the total horizontal side combines to 4+8 = 8. This is the segment HP as shown in the diagram below. I've also added point Q to form triangle HPQ. This is a right triangle so we can find the hypotenuse QH

Use the pythagorean theorem to find QH

a^2 + b^2 = c^2

(HP)^2 + (PQ)^2 = (QH)^2

8^2 + 4^2 = (QH)^2

(QH)^2 = 64 + 16

(QH)^2 = 80

QH = sqrt(80)

Now we use segment QH to find the length of segment EH. Focus on triangle HQE, which is also a right triangle (right angle at point Q). Use the pythagorean theorem again

a^2 + b^2 = c^2

(QH)^2 + (QE)^2 = (EH)^2

(EH)^2 = (QH)^2 + (QE)^2

(EH)^2 = (sqrt(80))^2 + (4)^2

(EH)^2 = 80 + 16

(EH)^2 = 96

EH = sqrt(96)

EH = sqrt(16*6)

EH = sqrt(16)*sqrt(6)

EH = 4*sqrt(6), showing the answer is choice C

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A shortcut is to use the space diagonal formula. As the name suggests, a space diagonal is one that goes through the solid space (rather than stay entirely on a single face; which you could possibly refer to as a planar diagonal or face diagonal).

The space diagonal formula is

d = sqrt(a^2+b^2+c^2)

which is effectively the 3D version of the pythagorean theorem, or a variant of such.

We have a = HP = 8, b = PQ = 4, and c = QE = 4 which leads to...

d = sqrt(a^2+b^2+c^2)

d = sqrt(8^2+4^2+4^2)

d = sqrt(96)

d = sqrt(16*6)

d = sqrt(16)*sqrt(6)

d = 4*sqrt(6), we get the same answer as before

The space diagonal formula being "pythagorean" in nature isn't a coincidence. Repeated uses of the pythagorean theorem is exactly why this is.