Question

Tony bowled 135 and 145 in his first two games. write and solve a compound inequality to find the possible values for a third game that would give him an average between 120 and 130, inclusive.
a.) 120 <= 135 +145+n/3 <=145; 120 <= n <= 140
b.) 135 <= 120 + 140 + n/3 <= 145; 80 <= n <= 85
c.) 120 < 135 + 145 + n/3 < 130; 80 < n < 110
d.) 120 <= 135 + 145 + n/3 <= 130; 80 <= n <= 110

Answer 1

The average has to be at least 120 and at most 130
To calculate the average we need the sum of all values divided by the number of values, in this case, three (135, 145 and the third result).
120 ≤ (135 + 145 + n)/3 ≤ 130

In inequalities like this, what we change in one side, must be changed in the othe rside as well.
360 ≤ 280 + n ≤ 390
80 ≤ n ≤ 110