When a mixture of starch and amylase is tested with a solution of iodine in potassium iodide, a blue-black colour is initially observed. However, when tested after one minute, the blue-black colour is no longer observed. This is due to the formation of
Mathematics
The triangle ABC above shows the angle of elevation of the top, B, of a tower, BC, from A, to be 30°. AB = 40 m. The length of BC is