Please solve; help is appreciated

The brain volumes (cm cubed) of 50 brains vary from a low of 904 cm cubed to a high of 1488 cm cubed. use the range rule of thumb to estimate the standard deviation s and compare the result to the exact standard deviation of 175.5 cm cubed, assuming the estimate is accurate if it is within 15 cm cubed

Is the square root of 4 plus the square root of 16 rational?

Aline that intersects one of two parallel lines intersects the other also always sometimes never