Probability that the first 2 of the friends to show up to the movie are friends he has known since kindergarten but the third not is 1/10
Total friends = 10
Friends from kindergarten = 4
Probability is the chance that a given event will occur. Probability of an event lies within 0 to 1
P(E) = Favourable outcomes / Total outcomes
Probability of getting 1st friend from kindergarten = 4/10
Probability of getting 2nd friend from kindergarten = 3/9
Probability of getting 3rd friend not from kindergarten = 6/8
Since all these probabilities are independent, We can use Multiplicative identity. Thus,
Required probability is 4/10 * 3/9 * 6/8
= 1/10
Thus, Probability that the first 2 of the friends to show up to the movie are friends he has known since kindergarten but the third not is 1/10
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Carry out the mult.: f(x) = -[x^2 - 21x + 9x - 189]
Combine like terms: f(x) = -[x^2 - 12x - 189]
Eliminate the brackets [ ]: f(x) = -x^2 + 12x + 189
Identify coefficients a, b and c: a= -1, b=12, c=189
The equation of the axis of symmetry is x = -b/(2a), which here equals
x = -(12)/[2(-1)], or x = 6
This is also the x-coordinate of the vertex. Plug x=6 into the original equation to calculate the y-coordinate.
it equals <span>(−<span>12</span>)</span> because <span><span>cos<span>(<span>60∘</span>)</span></span>=<span>12</span></span>
Explanation:
The reference angle for <span>240∘</span> is <span>60∘</span> (since <span><span>240∘</span>=<span>180∘</span>+<span>60∘</span></span>)
<span>60∘</span> is an angle of one of the standard triangles with
<span><span>cos<span>(<span>60∘</span>)</span></span>=<span>12</span></span>
<span>240∘</span> is in the 3rd quadrant so (either by CAST or noting that the "x-side" of the associate triangle is negative)
<span><span>cos<span>(<span>240∘</span>)</span></span>=−<span>cos<span>(<span>60∘</span>)</span></span></span>
<span><span>cos<span>(<span>240∘</span>)</span></span>=−<span><span>12</span></span></span>
Let the number of apples be x and that of pears be y, then:
0.64x + 0.45y = 5.26 . . . (1)
0.32x + 0.39y = 3.62 . . . (2)
(2) x 2 => 0.64x + 0.78y = 7.24 . . . (3)
(1) - (3) => -0.33y = -1.98
y = -1.98 / -0.33 = 6
From (2), 0.32x + 0.39(6) = 3.62
0.32x = 3.62 - 2.34 = 1.28
x = 1.28 / 0.32 = 4
Therefore, he bought 4 apples and 6 pears.