Brainercise: Mango Chicken edition
Lorène’s answer (which I agree with) to last week’s brainteaser is comment #4. Thanks Lorène!
My family and I had dinner at New Malaysia in Chinatown. They’re goooood. We ordered a bunch of different things, but that day the best thing I had was the Mango Chicken – spicy, but not too spicy, with a little sweetness going on from the mango, and a balance of other flavors, very tender chicken…it was really good. They also make this lychee drink there that I really like.
Anyway, my sister’s friend was there with us that night, and he told us a brainteaser. Here go you:
balance scale
There are 9 balls. 8 of them have the same weight, but 1 of them is heavier than the rest. Except for their weights, the balls look exactly the same – no difference whatsoever in appearance. The only difference is the weight. You have a balance scale and are allowed to use the scale a maximum of TWO times. You can weigh any combination of balls you like, in any order, as long as you make no more than 2 weighings. Given these conditions, how can you figure out which is the heavy ball?
Audrey
February 27, 2009my guess (note that 1a and 1b are alternative outcomes, and so are 2a and 2b):
STEP 1. weigh any 3 against another 3.
1a. if they are the same weight, then the heavier ball is in the last 3 that have not been weighed.
1b. if one side is heavier, the heavier ball is one of those 3 in the heavier side.
STEP 2. out of the group of 3 balls which contains the heavier ball, weigh any one ball against another ball.
2a. if they are the same weight, the heaviest ball is the third ball, the one not on the scale.
2b. if they are not the same weight, you will be able to tell which of the 2 is the heavier one; that is the heavier ball.
Cheers!