In ΔABC, a line is drawn parallel to BC to meet sides AB and AC in D and E respectively. If the area of the ΔADE is 19 times area of the ΔABC, then the value of ADAB is equal to:
By theorem on ratio of areas of similar triangles, we get
A(△ADE)A(△ABC)=(ADDB)2
∴19=AD2DB2
∴ADDB=13.