Area Of Quadrilateral

The area of the quadrilateral formed by the points (2, 9), (4, 5), (6, 9) and (–2, 5) is? I had a formula for calulating the area. 2*Area = (x1y2-x2y1) + (x2y3-x3y2) + (x3y4-x4y3) + (x4y1-x1y4) But, is there any other simple way for solving this? Thanks in advance.

Problem on Circles

Hello all, Please help me in solving this problem. A line MN is 10 meters in length and is tangent to one of 2 concentric circles at point A. If it is given that the radii of both the circles are integers, then what is the radius of the inner circle? Thanks in advance.

Triangles problem

Hello all, I felt that the data provided in the below problem is insufficient to solve it. Someone help me in fixing it. A triangular garden is to be enclosed inside 3 straight fences. Raju started running at the same speed on the 3 sides of the proposed boundary of the garden and discovered that it took 48 minutes, 102 minutes and 90 minutes to traverse the garden's smallest, largest and the other 3rd sides respectively. Later, the coverage area of the park was reduced. So, leaving the shortest side alike, the length of the third side was reduced by 60% of its original size and the fence was constructed on this reduced size along the direction of the original side. The longest side is then modified accordingly so that the park still remained triangular in shape. How much time will Raju take to run along the boundary of the garden thus formed? Thanks in advance.

Geometry (Triangles)

Hello all, I have 2 different problems. Someone, please help me in these problems. (1) DABC is right angled at A. D is a point on AB such that CD=1. AE is the altitude from A to BC. If BD=BE=1, then the length of AD equals = ? (2) In DABC, side AB=20, AC=11 & BC=13. The diameter of the semicircle inscribed in ABC, whose diameter lies on AB and that is tangent to AC & BC is. Thanks in advance.

Geometry question

Help in solving the following two questions Q1. Ten points are marked on a straight line and eleven points are marked on another straight line. How many triangles can be constructed with vertices from among the above points? 1. 495 2. 550 3. 1045 4. 2475 Q2. Ten points are marked on a straight line and eleven points are marked on another straight line which is parallel to the first line. How many rectangles can be constructed with vertices from among the above points?