To solve the joint variation question we proceed as follows: let the strength be p, the width be w, and thickness be t. thus: p=kwt where k is the constant of proportionality. p=2520 when w=7 and t=3 thus 2520=7*3*k hence k=120 thus the formula for variation is: p=120wt hence the value of p when w=2 in and t=1 in will be: p=120*2*1 p=240 pounds
