Questimate! from Motion Math is a enjoyable estimation game in which you create off-the-wall questions and try to estimate their answers. It's a challenge you can play alone or against others in either pass-n-play mode or Gamecenter mode.
As its name implies, Questimate! is based on quests that are comprised of a series of questions. You are given three lives, which allows you to make three mistakes as you progress along a quest. It's a game of estimates so you don't have to be perfect, but you do have to answer most of the questions in a quest reasonably well if you want to win. The app includes a free intro quest, with additional quests available via an in-app purchase of coins.
When you start a new game, you are prompted to build a question by combining several phrases like "How many microwave ovens", "would be as long as" and "a household ladder?" Once you've formed your question, you then must estimate the answer on a number line. The app will score your answer based on how close your estimate is to the actual answer. The more accurate your answer, the more points you will earn. Points will net you hints and power-ups, which you can redeem when you need help answering a hard question. If your answer is way off, you will lose one life. The goal of the game is to finish each quest before you lose all three of your lives, so you want to estimate your answer with accuracy.
I let my 12-year-old son and my 11-year-old daughter play Questimate!, and the reviews were mixed. My son is a visual learner and spatially aware, while my daughter is not. She just guessed at the answers (and was usually way off), while my son was walking around the kitchen sizing up the microwave to see how many he could fit on our ladder. He loved the game and its offbeat questions, while my daughter was ambivalent about the questions, but took delight in how far off her estimates were.
Questimate! is a barrel of fun for older children and young-at-heart adults who enjoy comparing items and making estimates. It is available for free from the iOS App Store, though it does require an in-app purchase of coins to unlock levels.