What Makes a Number Sentence True or False? 03:29 minutes

Video Transcript

Transcript What Makes a Number Sentence True or False?

Late one night, Zippy and his dog Strumpy are out for a walk when all of a sudden, Strumpy catches a scent and takes off! It looks like he ran into the old, abandoned amusement park. Hey...those look like...paw prints in the mud! But it's getting dark...so, it's hard to tell. If only there was a way to turn these lights on. That's when Zippy sees an electrical box. But there are some strange numbers and symbols written on it. It looks like in order to find his dog and solve this mystery. Zippy is going to need to figure out what makes a number sentence true or false. Take a look at the three number sentences written on the electrical box… Do you see anything strange about them? Some of these number sentences are definitely not true. But which ones? The first number sentence reads "4 + 6 is less than 9".

But 4 + 6 is equal to 10, and 10 is greater than 9, so this number sentence is definitely false. Next: 3 times 6 is equal to 18. This number sentence is true because the expressions on both sides of the equal sign are equal to 18. Finally, 22 is greater than or equal to 11 plus 12.

Well, 11 plus 12 is equal to 23, so this last number sentence is false. But how does this help Zippy find Strumpy? Zippy flips the inequality symbols to make all three number sentences true and look there, the lights turned on! But wait a second. What’s that noise? That’s definitely not Strumpy! Let's get out of here! Back at the entrance he hears a bark coming from the direction of the Ferris Wheel. How did Strumpy get up there? Let´s get him down! Zippy finds the ferris wheel's control panel and, just like the electrical box, there are three number sentences written on it but these number sentences have variables. How can he figure out which ones are true and false if he doesn't have a number to substitute in for 'x'? Zippy finds a weird punch card with the number 10 written on it just lying next to the control panel. Maybe this will help him find Strumpy? Maybe if we substitute 10 in for 'x', we can make one of these number sentences true! Let's try it out. If we substitute 10 in for 'x' in the first sentence we get 25 minus 10 is less than 15. Since 15 is not less than 15, this number sentence is false. If we substitute 10 in the next sentence. We get 13 is greater than or equal to 10 plus 4, or 14.

13 is not greater than or equal to 14, so this is false too. Last chance 70 divided by 10 is equal to 7. Yes! That's a true number sentence! Zippy inserts the number 10 card and is about to turn on the Ferris Wheel but wait a minute it looks like somebody wants to help... Oh. Well that was nice of him. Maybe that swamp monster isn’t so bad after all maybe the whole time, he just wanted to be swamp friends.