The radii of two concentric circles are 17 cm and 25 cm. a straight line PQRS intersects the larger circle at the points P and S and intersects the smaller circle at the points Q and R. If QR = 16 cm, then the length (in cm.) of PS is 

ABC is a triangle in which DE || BC and AD: DB = 5: 4. Then DE: BC is

ABCD is a cyclic quadrilateral. AB and DC when produced meet at P, If PA 8 cm, PB = 6, PC = 4 cm, then the length (in cm) of PD is

if θ is acute angle and sin (θ+18⁰) = 1/2, then the value of θ in circular measure is :

The length of two chords AB and AC of a circle are 8 cm and 6 cm and ∠BAC=90º, then the radius of circle is

In a regular polygon, the exterior and interior angles are in the ration 1:4.The number of sides of the polygon is

In a triangle, if three altitudes are equal, then the triangle is 

If ABC is an equilateral triangle and D is a point on BC such that AD⊥BC, then