SAT Question of the Day

From SAT Question of the Day...

Read the following SAT test question, then select your answer.

If a, b, and c are numbers such that a/b=3 and b/c=7 , then (a+b)/(b+c) is equal to which of the following?

A. 7/2
B. 7/8
C. 3/7
D. 1/7
E. 21

College Board solution:

From is implied that (1)

And from is implied that (2)

If we multiply (1) and (2) together, we have that ( b is canceled out).

There's an easier way. Just get a fraction that has just b and c.

a=3b
b=7c

so (a+b)/(b+c) = ...

3b+b
----- =
7c+c

4b
--- = 1/2 (b/c)
8c

b/c=7, so the answer is 1/2(7) = 7/2


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