Question 55
In an isosceles trapezoid $ABCD$ with larger base $AB$, the diagonals are divided by their intersection point $O$ into parts proportional to the numbers 1 and 3. Knowing that the area of triangle $BOC$ is 15, what is the area of the whole trapezoid?
(A) 60
(B) 75
(C) 80
(D) 90
(E) 105.
(A) 60
(B) 75
(C) 80
(D) 90
(E) 105.