Practice Quiz

SAT Math Practice Exam

Category - Mathematics - Hard

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If x+y=6, y+z=7 and z+x=9, what is the average(arithmetic mean) of x, y and z?
  1. 11/3
  2. 22/3
  3. 11
  4. 22
Explanation
Answer A - Add the three equations
x+y=6
y+z=7
z+x=9
__________
2x +2y +2z =22
x+y+z = 11
or (x=y+z)/3 = 11/3


Key takeaway: First have a close look at the pattern of the give equations for any simpleway to attack such problems. Sometimes simply adding or subtracting the equations may yield the desired result.
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