Investorship Financial Education Foundation
Answers to the Questions from Chapter 1
QUESTION 1: The total cost of a bat and a ball is $1.10. The bat costs one dollar more than the ball. How much does the ball cost?
ANSWER: Most say ten cents because it seems so obvious: just subtract one number from the other ($1.10 minus $1.00) and you get $0.10. But that’s wrong! Think about the ten-cent answer. If the bat cost one dollar more than a ten-cent ball, then the bat would cost $1.10. Now if you add a ten-cent ball to a $1.10 bat the total cost for both is $1.20. But the question started off saying the two together were $1.10. Therefore, the ball cannot cost ten cents. Although the cost of the ball can be calculated algebraically, it’s probably easier to just try another number as the cost of the ball. Since you now know that ten cents is too much, try a smaller number. Try five cents for example. That would make the bat cost $1.05 (one dollar more than the five-cent ball, as stated in the question). Add that five-cent ball to the $1.05 bat and voilà: $1.10 (the number given in the question). Therefore, the ball must cost five cents.
QUESTION 2: Mary’s father has five daughters. The names of the first four daughters are: Nana, Nene, Nini, and Nono. What’s the name of the fifth daughter?
ANSWER: Most people say Nunu, but the correct answer is Mary. As with the previous question, we tend to let our intuition take over making further thought seem unnecessary. Why spend time when the answer seems so obvious? As normal human beings, we tend to spot trends or patterns—and extend them. In this case, the vowels and consonants in the four names led most of us to conclude that the pattern would continue to the next logical combination, Nunu. But the question itself contained the answer: Mary’s father’s fifth daughter is named Mary.
QUESTION 3: You are a participant in a race on a straight track. You overtake the second person. What position are you in?
ANSWER: Most people say the answer is first place, but the correct answer is second. Again, our affinity for logical patterns and sequences makes it easy jump to the intuitive but incorrect answer. Because “first” precedes “second” we rely on our intuition and fail to calculate what is actually happening in this scenario. If we have only displaced the runner in second place, then we are now in second place and the leader is still ahead.
QUESTION 4: You overtake the last person in the same race. What position are you in?
ANSWER: Most people say, “last place,” which is impossible. There can be no answer because no one in a race can be behind the last person in a race. We intuitively jump to the seemingly logical answer, and are disinclined to spend energy unnecessarily, so the easier mental shortcut is often substituted when no correct answer is possible.
QUESTION 5: A person who cannot speak goes into a shop to buy a toothbrush. By imitating the action of brushing his teeth, he successfully expresses his need to the shopkeeper and makes the purchase. Then, a person who is blind comes into the same shop to buy a pair of protective sunglasses. How does she indicate to the shopkeeper what she wants to buy?
ANSWER: Most people say that they imitate the action of putting on sunglasses, which is incorrect. The correct answer is that they ask the storekeeper for a pair of sunglasses! In the first scenario of the story, the person who could not speak mimed what they wanted. So, we are predisposed to try and make the two stories consistent, rather than slowing down and thinking about what an actual blind individual is capable of doing. They have no speaking impediment, so they just ask.
Don’t be frustrated if you answered any of these questions incorrectly. Most people do! In fact, some answer them all incorrectly. Giving the intuitive-but-wrong answer simply proves you have a functioning, System 1 brain, as we all do. All too often, however, many of the errors we make can be directly attributed to our failure to integrate System 2 thinking into the decision process.