Short answer: There is a "green" pigment in leaves of trees called "chlorophyll", and is needed for photosynthesis. Long answer: Colours are a property of the interaction between visible light, the surface of the object and our eyes, NOT a quality of the object itself. The colour you see is simply the wavelength of visible light least absorbed by the the object itself, and thus most reflected.... more

It would be 24th November 2019 if there were none. a) What are leap years? Every year that is exactly divisible by four is a leap year, EXCEPT for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 are not leap years, but the years 1600 and 2000 are. So 3 leap years every 400 years are... more

General equation of line y=mx+c 1. Find the gradient(m1) of the line. 2. Find the negative reciprocal(m2) of that: -1/m1(gradient) All lines with that negative reciprocal are perpendicular. (3.) If you want to find a particular perpendicular line, substitute, into general equation, the given (X, Y) coordinates and m2 (found in step 2), and use them to find c. This c will give you a unique equa... more

Profit = total revenue - total cost Revenue: 27 * 12 = 324 Cost : 25*12 = 300 Profit = 324 - 300 = 24 (rs)

Just to finally link Joseph's answer to the question, oxygen difluoride will thus change from liquid to solid state when chilled from -220°c to -230°c.