Which of the following is a true statement about perfect squares? 8. 8 = 16
13 · 13 = 2(13)
81 is a perfect square.
111 is a perfect square.
Big quiz please help

Anyone know? will mark brainliest if correct!

Sanya noticed that the temperature was falling at a steady rate of 1.4 degrees every hour from the time that she first checked her outdoor thermometer. by 6 a.m., the temperature had fallen 21 degrees. which expression can you use to find how many hours earlier she had first checked the thermometer?

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?