Police officer A patrols 36 streets in 4 hours. His colleague, officer B, patrols 55 streets in 5 hours. How many streets will both officers patrol in one hour?
Officer A patrols 36 streets / 4 hours = 
<gadget id="calculator">36/4</gadget>
<output>9</output>
9 streets/hour.
Officer B patrols 55 streets / 5 hours = 
<gadget id="calculator">55/5</gadget>
<output>11</output>
11 streets/hour.
Together officer A and B patrol 9 streets/hour + 11 streets/hour = 
<gadget id="calculator">9+11</gadget>
<output>20</output>
20 streets/hour.

<result>20</result>