SAT Math help- practice PSAT from collegeboard

Quix
Sat, 02 Aug 2008 18:12:58 +0000

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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.

20.E
You can use bigweights method, or you can do this.

Use porportions since both arcs share the same angle, bc their centers are the same.

r/6 = R+3/X
Cross multiply
6r+18 = rx
solve for X
6r+18/r = x.