Four. If the apples are A, B, and C, it’s possible that you could take out one A, one B and one C with three apples, but the fourth apple must be one of the three kinds.
Money is right above my reach, I’m barely staying out of The Emergency Room (It is right below me), Room #3 is to my left, Room #5 is to my right with a 5% interest rate.
The number 4 key on a QWERTY keyboard. $ is money, ER (an abbreviation for Emergency Room) are the two letters immediately below the number 4 key, the #/3 key is to the left and the 5/% key is to the right.
Mario is testing out a new car at the racetrack. His grandmother took it for a mile lap and averaged 30mph. How fast does Mario have to drive in the second lap to average 60mph for the two miles?
90mph is an alluring answer, but it’s impossible. At 90mph the second lap would take 40 seconds. If Grannie’s first lap at 30mph took 2 minutes, traveling 2 miles in 2 minutes and 40 seconds is an average speed of 45mph. Traveling an average speed of 60mph for 2 miles would take 2 minutes and since the grandma’s lap took all of those 2 minutes, even if Mario could break the sound barrier he wouldn’t be able to average 60mph.
A similar problem can be found in L.A. Graham’s Ingenious Mathematical Problems and Methods with a range of 1 to 9, but the principle remains the same – the numbers with the smallest difference produce the largest product. You start out with the highest two digits, 7 and 6, then attach 5 and 4, putting the smaller of the two digits with the larger number, giving you 74 and 65. The next two highest digits are 3 and 2, giving you 742 and 653. Finally, you add the 1 to the lower number. Page 80 has the details of that solution.
He was born on February 29th in a leap year. Consequently, in his 87 years, he only witnessed twenty-one of his actual birthdays. The other years there was no February 29th.