Eternity Async Tutoring

[Elliot]

@Eternity

@Elliot

If you want to increase a number by 28%, what do you do? What if you want to decrease by 5%? What about increasing by 350%?

You find 28% of that number. then add 28% to the original number. 28% of 100 is 28. Then you’d add 28 to 100 and you get 128. Same process with decreasing you’d just subtract. 5% of 50 is 2.5. So a decrease by 5% would be 50 - 2.5= 47.5. 350% of a number would be 3.5 times that number added to itself. 10 * 3.5 = 35. A 350% increase would be 45. I’m pretty sure that’s right, but something about increases or decreases about 100% feel weird in my head. A 10% increase in 100 to 110 feels fine. A 200% increase to 300 feels weird. I think my brain is skipping the increase part when its increasing over 100% so it subconsciously looks wrong. A 200% increase to 200 feels right even thought it isn’t.

That’s a good answer but there’s also a different way to do it that’s also worth knowing. If you want to increase 30 by 10%, you can do it without adding. Any ideas?

@Eternity

Yeah I guess another way to put it is these particular word problems I’m getting confused by. Or I did. Earlier this morning I did 10 problems for about 20 minutes and got none wrong. I also reviewed some chapter problems and was able to do them. One issue here I forgot to mention was with the associative property and percent increases and decreases. I understand it fine now, but previously I remember getting confused with certain word problems where I thought the order in which you did your percent increases and decreases mattered. When I saw that it didn’t matter, I understood the math but it wasn’t clicking cleanly for me (kinda like increases over 100%) until today.

Have you been reading LMD Async Tutoring and followed the math from that topic?

@Eternity

Here’s my own working after the fact (its only up to a point).

One thing I’d do differently is convert all percents to fractions immediately. It’s fine to include percents when initially setting up the problem (translating the words to math), but when you start calculating/simplifying I’d get rid of them.

@Eternity

its specifically rates where my brain turns to mush.

For those rate problems, you can start by writing down things you know (the pieces of information in the problem) and then brainstorming equations. Equations involve finding two different things that are equal. If they’re unequal but related in some clear way, you can make them equal, e.g. if something is triple the other thing, then add a division by 3 to get them equal. If you find a way to calculate something using other information, then that’s an equation too: calculating something means being equal to it.