Solution,
Change in water level is [tex]1\dfrac{1}{2}\ \text{inches}=\dfrac{3}{2}\ \text{inches}[/tex]
The water level of a lake fell by [tex]1\dfrac{1}{2}[/tex] inches during a [tex]1\dfrac{2}{3}\ \text{or}\ \dfrac{5}{3}[/tex]week-long dry spell.
Average rate at which the water level changed every week is given by :
[tex]R=\dfrac{1\dfrac{1}{2}}{1\dfrac{2}{3}}\\\\R=\dfrac{\dfrac{3}{2}}{\dfrac{5}{3}}\\\\R=\dfrac{3}{2}\times \dfrac{3}{5}\\R=\dfrac{9}{10}\\\\R=0.9[/tex]
Hence, the average rate is 0.9 every week.
