From my research a can of Campbell's Condensed Tomato Soup typically has dimensions where the radius is approximately 3.8 cm and its height approximately 10.8 cm. However there were many other dimensions so I just chose the most common one. The average road bike length is approximately 177 cm. One can measure the length of the bike in the picture with a ruler and the length of the can in the picture (which is the height as it’s sideways). Divide the length of the can by the length of the bike. Multiply that number by 177 to get the actual length of the can in cm. I will say three bikes fit alongside the length of the can so 177 cm times 3 equals 531 cm. Since the proportions are the same as a normal sized can, the radius of the water tank can is 531 times 3.8/10.8 which equals around 187 cm. Putting it all together the volume is π[(187)^2](531) which equals around 58 334 786 cm^3 = 58.334786 kL. This is more than enough water to put out an average house fire, since only several kL of water is needed. My experience doing this question initially wasn't fun since I couldn't find consistent values for the dimensions of the soup can. There were different versions of the cans and sometimes the dimensions given to me were for the box that contains them! The image of the water tank can was also taken at an angle so measuring it from side to side wasn't even. Thus I just approximated that three bikes fit across. This question made me relate to a typical question grade 10 students would do with scales and proportions, say finding approximately the distance between two city centres in real life. On the diagram a cm could represent 50 km. Students measure two dots representing the two city centres and find their distance, say 6 cm. So that means they are 300 km away. Other times you walk into a museum and there is a big display of a lego model representing ancient Rome. There might be a scale at the bottom so one is able to figure out approximately how big ancient Rome really was back then based on how big the model was.
As a more specific example, below are pictures I took on New Year's Eve 2018 at the Edmonton City Hall. It is a lego model of people (veterans, RCMP, politicians, citizens) at the Vimy Ridge Memorial. I was curious to know if this was to scale as I meticulously observed this work of art. I haven't personally been to the memorial site, but I hope to one day, remembering the victory for freedom the allies fought hard for. It's especially important now as we near Remembrance Day. To see if this is approximately to scale, you can measure the height of one lego human, which is 4 cm. The average human height is 170 cm. The actual twin pylons are 27 m = 2700 cm tall. The scale is 170/4 = 42.5, so when the the height of the lego memorial's twin pylons are measured, it should be around 2700/42.5 = 63.5 cm if this model is to scale. From what I recall, it was around that height, so the model is decently accruate. This problem is doable if we are actually allowed to carefully measure this lego structure with permission. Otherwise we will have to resort to using a photo and use its measurements of the lego human figures/twin pylons to find if the scale for the structure is consistent.