I need help with this algebra asap

What number produces an irrational number when multiplied by -1.25

Aline has a slope of 1/4 and passes through point (0.4,-1/2). what is the value of the y-intercept?

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