This math percentage problem makes NO SENSE to me?
Q: A number is increased by 80%, or 480. What is the original number?
Answers:
A) 267
400
C) 600
D) 2,400
I don't understand it at all. I don't like posting my questions online it feels like cheating but I'm really just stuck on this one and nobody's here atm to help me so... I'd appreciate anyone who can explain this problem to me.
Update:Thank you tycha it makes perfect sense now. The way the exam worded it confused me.
Comments
80% of the number is 480.
80/100 = 480/x
80x = 480 * 100
x = 48000/80
x = 600
BTW, if someone give you the answer, like x = 600, then that's cheating. If someone guides you through doing the problem so that now you understand it and can do others on your own, that's not cheating. Don't be afraid to ask for help. I'm on IM if you need a walkthrough.
80% of the number is 480.
So,be the original number =x
80%*x=480
or,80*x/100=480
or,4x/5=480
:.x=480*5/4=600 Ans.
What the question is saying that increasing x by 80% is the same thing as adding 480 to it.
x + 80% of x = x + 480
rewriting this remember % means /100 and of means multiplied by.
x + (80/100) * x = x + 480
x + 80x/100 = x + 480
subtracting x from both sides
x-x + 80x/100 = 480
0 + 80x/100 = 480
80x/100 = 480 <-- this is where most people would start but I wanted to spell it out for you why this is the case as you said you were having difficulties.
multiply both sides by 100
80x = 48000
divide both sides by 80
x = 48000/80
simplify by dividing top and bottom by 10
x = 4800/8 but hang on isn't 48 on our 8 times table? 6*8 = 48
x = 600 <-- If you hadn't spotted 6*8=48 it's okay to use a calculator on this type of question I'm sure.
A) 266.67 (approximated)
Many students of mine have difficulties with percent
I'll try to explain
Incrasing by 80%
if the number was 100 it becomes 180
if the number is ??? it becomes 480
there is a proportion to write down and solve
100:180=x:480
x = 480*100/180 = 800/3
x = 266.66666.....
I hope this helps
This one you have to go backwards on.
Instead of a problem asking what the percentage of something is, like...
50% of 100.
Multiply 100 by .5 and you get 50.
let n be the number you're trying to find out
The problem is "Multiply n by .8 and you get 480."
Inverse operations. Take 480 and divide it by .8 to get the missing value
80% increase means when 100 is original no, increased by 80% = 180
now increased no =480 so ratio goes thisway = increased no /original no
180 /100 = 480/ x
180 * x = 480 * 100
x = 480* 100 / 180
we get 266. 66------ = 267
if you are stuck on a test,
you can try the given answers ...
A: 267 * .8 = 213.6 (too low)
B: 400 * .8 = 320 (too low)
C: 600 * .8 = 480 (winner)