If a line has a slope of - 5/2, then a perpendicular line would have a slope of 5/2.

true or false and why

False, since if there are two perpendicular lines with gradients m1 and m2, then m1*m2 = - 1.

Taking this example - 5/2 multiplied by 5/2 is equal to - 25/4, which is not equal to - 1.

To find the actual gradient of the perpendicular line you would have to divide - 1 by - 5/2, which gives you 2/5.