SumChallenge is a small application I developed and released in 2014.
Description from the Apple Store
Do you think you are the best at mental calculation? You aren't that good, but you like challenge yourself? You are nostalgic of your primary school's mathematic session? So, this app is for you.
Train your brain and challenge all your friends. Solves the equations as fast as possible to get the best score and become the number one of the leaderboard. Be the king of additions, and prove to the word you are the best.