V ( cylinder ) = r² π h
V ( cone ) = 1/3 r² π h
A cone that fits exactly inside the cylinder has the volume:
V ( cone ) = 1/3 V ( cylinder = 1/3 · 81 = 27 ft³
B. All rectangles are parallelograms! And C. All equilateral triangles are isosceles! :-)
Looks like a badly encoded/decoded symbol. It's supposed to be a minus sign, so you're asked to find the expectation of 2<em>X </em>² - <em>Y</em>.
If you don't know how <em>X</em> or <em>Y</em> are distributed, but you know E[<em>X</em> ²] and E[<em>Y</em>], then it's as simple as distributing the expectation over the sum:
E[2<em>X </em>² - <em>Y</em>] = 2 E[<em>X </em>²] - E[<em>Y</em>]
Or, if you're given the expectation and variance of <em>X</em>, you have
Var[<em>X</em>] = E[<em>X</em> ²] - E[<em>X</em>]²
→ E[2<em>X </em>² - <em>Y</em>] = 2 (Var[<em>X</em>] + E[<em>X</em>]²) - E[<em>Y</em>]
Otherwise, you may be given the density function, or joint density, in which case you can determine the expectations by computing an integral or sum.
Well, we can substitute the variables and get :
9(21)+3(3)(21)+12
Then we simplify :
189+189+12
To get :
390 flowers
By the way you might be confused like I was for it said "a cake topping," whilst I assumed all tables had cake toppings which is untrue and I nearly ended up with 630 flowers.
15 + 20 equals to 35, 60 - 35 equals to 25 so so his total journey is 1 hour
