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Nyla
07-18-2013, 03:56 PM
SAT math average statistics

Could you help with the following question:
"The average of x and y is 10 and the average of x,y and z is 15. Find the value of z."

Thanks in advance!!:):)

Jack
07-18-2013, 04:02 PM
SAT math average question


"The average of x and y is 10 and the average of x,y and z is 15. Find the value of z."

The arithmetic mean, also known as average, is the sum of all the values in a list of numerical values divided by the number of items in the list.

"The average of x and y is 10" : \frac{x+y}{2}=10 \Rightarrow x+y=20 (1)

"the average of x,y and z is 15" : \frac{x+y+z}{3}=15 \Rightarrow x+y+z=45 (2)

Subtracting (1) and (2) you have that z=25

Nyla
07-18-2013, 04:03 PM
Thanks Jack!!