30- second challenge
JUST follow the instructions from left to right, starting with the number given to reach an answer at the end of the row. Set your own 30- second challenge: for the very young or arithmetically rusty, you have 30 seconds for the BEGINNER task. For a greater challenge, try BEGINNER and INTERMEDIATE in 30 seconds. True mental gymnasts should try INTERMEDIATE and ADVANCED in 30 seconds together.