SAT Math: Central Tendency 2

1. Four truck drivers average using 75 gallons of fuel driving from San Francisco to Los Angeles. Three of the truck drivers used an average of 70 gallons combined. How many gallons of fuel did the fourth driver use?

$75$

$70$

$90$

$80$

2. If $x$ is the average (arithmetic mean) of $a$ and $7$ , $y$ is the average of $3a$ and $13$ , and $z$ is the average of $4a$ and $16$ , what is the average of $x$ , $y$ , and $z$ , in terms of $a$ ?

$2(2a+9)$

$8a+36$

$\dfrac{2(2a+9)}{3}$

$\dfrac{4(2a+9)}{3}$

Based on the histogram above, of the following, which is closest to the average (arithmetic mean) number of peaches per tree?

$3$

$30$

$20$

$35$

The table above lists the heights, to the nearest inch, of fifteen shrubs. The outlier measurement of 20 inches is an error. Of the mean, median, and range of the values listed, which will change the most if the 20 inches measurement is removed from the data?

Median

Range

Mean

They will all change by the same amount

5. A restaurant receives customer satisfaction ratings between 0 and 100 (inclusive). In the first 20 ratings the restaurant received, the average (arithmetic mean) of the ratings was 80. What is the lowest rating the restaurant can receive for the 21st rating and still be able to have an average rating of at least 85 for the first 30 ratings?

$50$

$70$

$85$

$90$

6. Kyle tried to calculate the average of his 9 Calculus test scores. He accidentally divided the correct sum of all his test scores by 10, yielding 81. What is Kyle's actual average test score?

$80$

$85$

$88$

$90$