Answer
The mean strength of the concrete is 3670 psi.
The median strength of the concrete is 3830 psi.
The mode strength of the concrete is 4090 psi.
Work Step by Step
The data in ascending order: 2940, 3100, 3200, 3780, 3830, 3960, 4040, 4090, 4090.
The mean: $\frac{2940+3100+3200+3780+3830+3960+4040+4090+4090}{9}=3670$
There are 9 values. So, the median is the 5th value: 3830.
The mode strength is 4090 because it appears twice and the others appear once.
