Math Is Fun Forum

kiddy3

Guest

percenntage question

This is probably easy for you guys . I just dont get how you work this question out, hope you can help me thank you .
If 20% of a number is 8 what is the number?.

Stanley_Marsh

Member

Registered: 2006-12-13

Posts: 345

Re: percenntage question

If thinking backward is hard , then assume that number is x and you will get this

Last edited by Stanley_Marsh (2007-04-03 02:34:21)

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Numbers are the essence of the Universe

jagabandhu

Member

Registered: 2007-03-30

Posts: 6

Re: percenntage question

alternative way is

20% of the number is 8

1% of the number is 8/20

100% of the number is (8/20)*100 = 40

[snip email]

Last edited by MathsIsFun (2007-04-03 09:37:58)

pandapatrol26

Member

Registered: 2007-04-03

Posts: 3

Re: percenntage question

umm if you just rewrite 20% in decimal form, which is .02 its much easier this way.
anyway, you need a variable since you're solving for a number, so .02 (OF) what number gives you 8?
so here: .02x=8

technically you don't know what x is, that's what you're finding out. you know if you multiply .02 of a number you get 20% of it right? so this is the same thing, except you set it equal to eight because that's what its equal to. divide 8 by .02 and you should get 40.

Devantè

Real Member

Registered: 2006-07-14

Posts: 6,400

Re: percenntage question

umm if you just rewrite 20% in decimal form, which is .02 its much easier this way.
anyway, you need a variable since you're solving for a number, so .02 (OF) what number gives you 8?
so here: .02x=8

technically you don't know what x is, that's what you're finding out. you know if you multiply .02 of a number you get 20% of it right? so this is the same thing, except you set it equal to eight because that's what its equal to. divide 8 by .02 and you should get 40.

Umm, 8 ÷ 0.02 ≠ 40.

I think you meant 20% = 0.2 and no 0.02, otherwise that'd be 2%.

So, 8 ÷ 0.2 = 40.

pi man

Member

Registered: 2006-07-06

Posts: 251

Re: percenntage question

Here's the way I was taught:

Cross-multiply to get 20x = 800.   Divide both sides by 20 to get x = 40.

pandapatrol26

Member

Registered: 2007-04-03

Posts: 3

Re: percenntage question

umm if you just rewrite 20% in decimal form, which is .02 its much easier this way.
anyway, you need a variable since you're solving for a number, so .02 (OF) what number gives you 8?
so here: .02x=8

technically you don't know what x is, that's what you're finding out. you know if you multiply .02 of a number you get 20% of it right? so this is the same thing, except you set it equal to eight because that's what its equal to. divide 8 by .02 and you should get 40.

Umm, 8 ÷ 0.02 ≠ 40.

I think you meant 20% = 0.2 and no 0.02, otherwise that'd be 2%.

So, 8 ÷ 0.2 = 40.

yeah my bad