Answer
\begin{array}{c}& \textbf{Watts per Hour} & \textbf{Frequency}
\\\hline & \text{54-62} & \text{7}
\\ & \text{63-71} & \text{6}
\\ & \text{72-80} & \text{8}
\\ & \text{81-89} & \text{4}
\\ & \text{90-98} & \text{1}
\\ & \text{99-107} & \text{3}
\\ & \text{108-116} & \text{1}
\end{array}
Work Step by Step
Find the width of each class by subtracting the lowest value from the highest. Divide the difference by 7, as 7 classes were specified in the instructions. Round up to determine the width.
$\frac{110-54}{7}=\frac{56}{7}=8$
Round up to 9. Note that rounding up is required even when the quotient is a whole number.
The lowest value is 54. Add 9 to each lower limit to find the next lower limit in the table. The upper limit will be one less than the lower limit that follows.
$54+9=63$
$63+9=72$
$72+9=81$
$81+9=90$
$90+9=99$
$99+9=108$
$108+9=117$ (Computed only to find the final upper limit)
