# Tutor profile: Joshua S.

## Questions

### Subject: Discrete Math

Texas Hold 'em is a poker game played where you are dealt two cards from a deck of 52 cards. How many different two card combinations exist?

We use the combination formula C(n,r) = n! / (r!*(n-r)!) where n= 52 and r=2 combinations = 52! / (2!*50!) = 52*51/2 =1326

### Subject: Statistics

Given observations 5, 7, 11, 15, 25 determine the mean and sample standard deviation

mean = sum of observations divided by the number of observations mean = (5+7+11+15+25)/5 = 63/5= 12.6 Sample Standard deviation = Square root {(sum of [(observation-mean)^2] / (number of observations - 1)} = Square root {(5-12.6)^2+(7-12.6)^2+(11-12.6)^2+(15-12.6)^2+(25-12.6)^2)/(5-1)} = Square root { (57.76+31.36+2.56+5.76+153.76) / 4)} = Square root { 250.84/4} = Square root (62.71) = 7.919

### Subject: Algebra

Solve for X 4X^2-10x-5=0

Using the quadratic equation, x=(-b +/- (b^2 - 4ac)^.5) / (2a) x= (10 +/- (10^2 - 4*4*-5)^.5) / (2*4) x= (10 +/- (100 - -80)^.5) / (8) x= (10 +/- 180^.5)/8 x= (10 +/- 13.42)/8 x= (2.9275, -.4275)

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