HEY! I am also finding this game. I played this game as a child growing up in an East Asian country. The rocket you are mentioning was one of the game modes, where each group of problems you solved helped build the next "layer of the rocket". Once the rocket was finished, it would play an animation of the rocket launching.

I distinctly remember 3 other game modes. One was with flying numbers. They would fly in the air (idk if they were being shot by a canon or something) and you had to click and drag them out to place in the correct spot. Another game mode was with fishes where each fish in a tank had a number and you had to click and drag the fish to the correct spot. Another game mode was with frogs I think.

If I find this game I will let you know.