Your child is now at that age when his mental capacities are growing in leaps and bounds. Whether it is in his language abilities, emotional development or even physical development, his skills are increasing on a daily basis. A lot of development has happened over the years in his mathematical skills. He not just knows his numbers but also simple fraction concepts like halves and quarters.
What you need to know
The more stimuli that he gets at home and outside, the faster and better will be his learning process. As of now his learning process is more inclined towards real life images and instances. He is still not able to grasp concepts that are hypothetical and theoretical. Use real life situations to reinforce the mathematical concept of fractions and he will understand it better. If you order in a pizza, your pizza is your learning board for fractions. Ask him to share half his cookie with you and he knows what is half.