Theory:

4. Conversion of ratio into per cent
 
We can convert the ratio into a percentage using the following method.
Example:
(i) \(a:b\)
 
=ab=[ab×100]%
  
(ii) \(3:8\)
 
=38=[38×100]%=3712%
 
5. Conversion of per cent into decimal
To convert the per cent to decimal, first change it to a fraction by dividing it by \(1000\) and remove the \(\%\) sign. Then put the decimal point accordingly.
\(a\%\)           \(= a/100\)        \(= 0.0a\)
(per cent)     (fraction)       (decimal)
Example:
(i) 35\(\%\)
 
\(=\) 35100
 
\(=\) 0.35
  
(ii) 87\(\%\)
 
\(=\) 87100
 
\(=\) 0.87\( \)
  
(iii) 18%
 
\(=\) 18 ·100
 
\(=\) 0.001\( \)
  
6. Conversion of decimal into a per cent
To convert decimal into a per cent, change it to fraction to remove decimal and then multiply it by \(100\) and put the \(\%\) sign.
Example:
(i) 5.6
 
\(=\) 5610
 
\(=\) [5610×100]%
 
\(=\) 560\(\%\)
 
(ii) 0.035
 
\(=\) 351000
 
\(=\) [351000×100]%
 
\(=\) 3.5\(\%\)