GMAT Practice Question: Last year members of a certain professional organization for teachers consisted of teachers from...
Question
Last year members of a certain professional organization for teachers consisted of teachers from 49 different school districts, with an average (arithmetic mean) of 9.8 schools per district. Last year the average number of teachers at these schools who were members of the organization was 22 . Which of the following is closest to the total number of members of the organization last year?
- 10^{7}
- 10^{6}
- 10^{5}
- 10^{4}
- 10^{3}
Topics: word problems, mean, calculations, approximations
Solution
Step 1
We translate the counts into the multiplication of the number of districts, the average number of schools per district, and the average number of teachers per school.
D = 49 S = 9.8 T = 22 Total = D \times S \times T
Step 2
Because the answer choices differ by orders of magnitude (powers of 10), we use rough estimation to simplify the multiplication.
49 \approx 50 9.8 \approx 10 22 \approx 20
Step 3
We multiply the approximate values to get the estimated total number of members.
50 \times 10 \times 20 = 10000
Answer
10^4
