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Studying for a test? Prepare with this lesson on Parts and wholes.
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Video transcript
Odie the octopus swam home. He swam at a constant speed. He plotted how far he'd gone every 1/7 of a second on the graph below. Not all octopi can create graphs, but Odie was no ordinary octopus. And actually, octopi are some of the smartest creatures on this planet. What was Odie's speed-- after probably dolphins and great apes and probably most primates, but they're still fairly smart, smarter than most fish. What was Odie's speed in meters per second? Note we use m/s to show the units of meters per second. All right. So to figure out speed in meters per second, we essentially need to divide distance in meters divided by time in seconds. So let's see if we can pull that off. So the easiest thing-- let me find a point that I can clearly read how far Odie has traveled. So it looks like this point right over here. It's clearly that the distance in meters is 4/7. So let me do that. So the distance in meters is 4/7, so I'll do that in the numerator. the distance in meters. Gee, I don't like that con-- well, I'll just go with this color. You know, the contrast with the white background is a little hard on the eye. And It took him 5/7 of a second to get there. So 4/7 meters-- actually, let me make sure I put the units here. 4/7 meters in 5/7 seconds. And so literally, we just need to divide 4/7 by 5/7, and we're going to get it in meters per second. So this is going to be the same thing as 4/7 over 5/7 meters per second. And 4/7 divided by 5/7 is the same thing as 4/7 times 7/5. So let me write that down. So 4/7 times 7/5. Dividing by a fraction is the same thing as multiplying by its reciprocal. So times 7/5, and we get this-- well, this 7 and this 7 cancel out, and you get 4 over 5. You could have also done that by multiplying the numerator and the denominator here by 7. If you multiply it by 7, multiply by 7, you would get 4/5. But either way, his speed in meters per second is 4/5 meters per second.