maths question

turnoffsaysthestar

Active member
If 30 % of ? =17 what is ? i have 2 ways of doing this but i am not sure if either are correct even though both work?
30/100 =17/? i can times both sides by? to get ?x30/100 =17 then x both sides by 100 and divide both sides by 30 to get ?=(17x100)/30 =56.66re.
or can i invert the problem so 100/30 =?/17 then times both sides by 17 to give me 17 x(100/30)=56.66re.

a little guidance would be appreciated
 
Both OK, but when I looked at it I simplified it, divided the 17 by 3 then multiplied by 10.
 
A logical path through the explanation:

17/3*10 = 56.67 (2dp)

If you know 30% of something, you can divide it by 3 to find 10%

30% = 17
(divide both sides by 3)
10% = 5.666666.....

Now you know 10% of something, so you can multiply it by 10 to get 100%

10% = 5.666666....
(multiply both sides by 10)
100% = 56. 66666...

Rounding to 2 decimal places give 56.67
 
When approached with this I divided the 17 by 30 to get 1%. Then you can multiply it by whatever number you wish to find a percentage

e.g 17/30 = 0.566. x 100 = 56.7 (100%) or x 70 = 39.6 (70%)
 
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