A perfect cake should have 25% cream and 75% bread. Oman bought material for a 5kg cake with 35% cream and 65% bread. How many more kg of bread should he buy if he wants to make a perfect cake?

A. 2kg
B. 2.5kg
C. 3kg
D. 4kg
E. 5kg

5 kg material has been bought with 35% cream and 65% bread
=> Amount of cream = 35% of 5 kg = 1.75 Kgs
=> Amount of bread = 65% of 5 kg = 3.25 Kgs (Another way would be 5-1.75 = 3.25Kgs)

Now we want to convert the ratio from 35%-65% to 25%-75% by buying more bread.
Here the amount of cream remains constant, hence 1.75kgs of cream should be 25% of the total amount.
Hence we need to have 75% of the bread. Now 75% is 3 times 25%, therefore the amount of bread we should have is 3 times the amount of cream

=> 3*1.75 = 5.25 kgs of bread is required

We have 3.25 kgs of bread and hence require 2 extra kgs of bread.

Hence A is the correct answer.

We can do it using mixtures concept..

65 _____100
___75___
25_____10

x=(5/25)*10
=2kg

Answer: A