### Home > APCALC > Chapter 12 > Lesson 12.1.3 > Problem12-38

12-38.

Multiple Choice: The function $f$ is continuous on the closed interval $[3, 9]$ and has values given in the table below.

 $x$ $f\left(x\right)$ $3$ $4$ $7$ $9$ $50$ $40$ $20$ $30$

Using the subintervals $[3, 4]$, $[4, 7]$, and $[7, 9]$, what is the trapezoidal approximation of $\int _ { 3 } ^ { 9 } f ( x ) d x$?

1. $160$

1. $185$

1. $200$

1. $210$

1. $300$

Be careful! The subintervals have different widths.

$\frac{1}{2}(f(3)+f(4))\cdot1+\frac{1}{2}(f(4)+f(7))\cdot3+\frac{1}{2}(f(7)+f(9))\cdot2$