The diameter is the distance from one side of a circle to the other, if you cross through the center. The circumference is the distance around the circle. The circumference is equal to two time pi time the radius (C=2*pi*r)
This is a combination in which you choose 4 from 10.
The formula is
combinations = 10! / 4! * (10-4)!
combinations = 10! / 4! * 6!
combinations = 10 * 9 * 8 * 7 * 6! / 4! * 6!
combinations = 10 * 9 * 8 * 7 / 4 * 3 * 2
combinations = 10 * 3 * 7
combinations = 210
Source:
http://www.1728.org/combinat.htm
160cm3
2/5 - 1/4 = 8/20 - 5/20 = 3/20
(3/20)t = 24
t = 160
Logarithmic functions are the inverses of exponential functions. The inverse of the exponential function y = ax is x = ay. The logarithmic function y = logax is defined to be equivalent to the exponential equation x = ay. y = logax only under the following conditions: x = ay, a > 0, and a≠1.