A trader finds that 30% of the wheat lying in godown A weighs exactly the same as 45% of the wheat lying in godown B. The stock in godown B is what per cent of the stock in godown A?

$0.30A=0.45B$, so $B=(30/45)A=(2/3)A=66$ 2/3% of A. Check with numbers: if $A=300$, then 30% of $A=90$, and $B$ must satisfy $0.45B=90$, giving $B=200$ - which is indeed two-thirds of 300. 150% is A as a per cent of $B$, the comparison the wrong way round; note that the SMALLER percentage goes with the LARGER stock. 15% is the 15-percentage-point gap and 75% simply adds the two rates.