petrol & population trick

Petrol is a mixture of what?learn with this trick.

Petrol is just like water H2O. Remember H2O, first H= hexane, second H=heptane and O= octain.

Population Density 2011- descending order of top 5 states

D.C.P   BIHARI k BANGLE mein bahoot log rahte hain...... trick to remember......D=Delhi.C=chandigarh.P=puducherry.B=bihar. BANGLE=west bangal