Answer: 10 + 1/2 spoons of vanilla.
Explanation:
This question says:
For 1kg of cake, we need 1/3 kg of flour and 3 spoons of vanilla.
How much vanilla do we need if we want to make a cake of 3 + 1/2 kg?
Ok, if for 1kg we need 3 spoons, then for (3 + 1/2)kg we need (3 + 1/2) times 3 spoons, this is:
(3 + 1/2)*3 spoons
=3*3 + 3/2 = 9 + 3/2 = 9 + 2/2 + 1/2 = 10 + 1/2
We need 10 + 1/2 spoons of vanilla.