Question 261416
Remember that the area of a triangle is A = 1/2 bh and your area is 140.  Therefore 140 = 1/2 bh.  If we double the base and double the height then we have 2b for the base and 2h for the height.   Then the area of the new triangle would be 1/2 * 2b*2h  or 2bh.  If we look at the original triangle with area 140 = 1/2bh then bh = 280 (by multiplying both sides by 2).  Now for the new triangle
A = 1/2 bh
  = 1/2 (2b)(2h)
  =2bh
we know that bh = 280 so 2(280) = 560square inches