Little Red Riding Hood goes to Grandma's house, which is located 4,900 m away to the East. If Red travels at a rate of 1.5 m/s, then how long will it take her to get to
Grandma's?

i guess that visual aids present persuasive examples to what you are presenting, some factors would be theme (does it fit with the color, information, what you are presenting), size (can you see it, is it a big enough span of data/information), and overall look of the visual aid.

hope this : )