<li>How many different 3-digit positive integers can be formed using the digits 2,3,4,5,6,7,8 if the units digit is 2 and no digit is repeated within an integer. </li>
</ol>
<p>A 12
B 15
C 24
D 30
E 36</p>
<li>The figure above shows a circle with radius r and center P and an arc of length 6. The radii shown are extended 3 units outside the circle. There is an arc of length x, which is part of a larger circle (not shown) also centered at P. what must x equal?</li>
</ol>
<p>theres 3 spaces _ _ _, the first one must be 2, so theres only 1 possible number available for the first slot. Thus 1 _ _, you have to more spaces, and since you already chose 1, you still have 6 numbers to choose from next, so its 6 for the next slot. 1 6 _, since you picked another number, you only have 5 choices left, so 5 will go at the end. 1 X 5 X 6= 30.</p>
<p>20.E
You can use bigweights method, or you can do this.</p>
<p>Use porportions since both arcs share the same angle, bc their centers are the same.</p>
<p>r/6 = R+3/X
Cross multiply
6r+18 = rx
solve for X
6r+18/r = x.</p>