1 kg of carbon requires 8/3 kg of oxygen for its complete combustion; therefore C kg of carbon will require C x 8/3 kg of oxygen which is equivalent to 2.66C kg of oxygen (considering up to two places of decimal).

As per the provisional results of Census 2011, total population of India is 1,21,01,93,422 which comprises of 62,37,24,248 males and 58,64,69,174 females with the sex ratio of 940 females per 1000 males.

Formula : N1/N2 =V1/V2 (Turns Ratio)
Where N is the number of turns in the coil and V is the voltage across the coil. Subscript 1 denotes primary side and subscript 2 denotes secondary side.
Therefore N2=N1*(V2/V1)
N2=1000*(400/250)
N2= 1600 turns.
1600 turns are required in the secondary coil to induce a voltage of 400V in the secondary side when the primary side voltage is 250V.
This is known as a step up transformer.