Well, this is a trapezoid. The formula for the area of a trapezoid is 1/2 the height times base one plus base two. In other words, 1/2 <em>h </em>x (base 1 + base 2)
So in this case, the two bases are 4 and 12. So we would add the two bases to get 16. Now, we have to half the height. 3 divided by 1/2 is 1.5. So we then do the last step which is multiplying the height by the two bases. So in other words, 1.5 times 16. And 1.5 times 16 is 24. Therefore, the answer is 24 sqaure kilometers.
