urgent help with my sons homework please

[scruffbag]

From each box pair up gradients of lines that are perpendicular to each other. box 1= third, -0.75, -0.3, -1/4, (minus1 over 4) 2 and a half , 3/4, -0.1, -2/3 box2= 4, -10, 3/2, [3 over 2] -4/3 [minus4 over 3], -2/5 [minus 2 over 5], 3, -3, and 1 1/3. [1 and a third.] i would really appreciate your help with this. my son is finding this very difficult. YOU ARE ALWAYS SO HELPFUL. THANK YOU!!

[Suzyboo]

The pairs of perpendicular gradients have to multiply to make -1 so for example, since 1/3 * -3 = -1 then the gradients 1/3 and -3 are a perpendicular pair. Your son needs to choose a number from each box so that the two numbers multiply to make -1 each time.