"If I asked you to calculate the inverse square root of 26 without a calculator, you’d probably be stuck for a while—and honestly, so would I."

Um, 5*2 is 25 and 6*2 is 36 so we know the square root of 26 is between thos two and likely a lot closer to 5.1.

And 1/5 = 0.2. The correct answer is .196 plus a few irrelevant digits.