I wonder if they do this on purpose?

[plonq]

This Mensa calendar seems to have one bad page per month.  I enjoy the little brain exercises every day, but ones like this drive me up the wall:

Eight chocolate bars plus six gumdrops cost 70¢.  You could buy seven gumdrops for the price of two chocolate bars.  How much change will you get back from $1.00 if you buy six of each?


The answer is: What fucking planet do these guys come from?  Let's just check their math.

8c + 6g = 70¢
7g = 2c ... 3.5g = c

Okay, now let's substitute.

8(3.5g) + 6g = 70¢ ... 28g + 6g = 70¢ ... 34g = 70¢

Unless I've done something wrong, 34 gumdrops cost 70¢

That means one gumdrop = 2.0588235294117647058823529411765¢

But hang on...

7g = 2c ... g = 2/7c
8c + 6(2/7c) = 70¢ ... 8c + 12/7c = 70¢ ... 68/7c = 70¢ ... 68c = $4.90

Therefore a chocolate bar costs 7.2058823529411764705882352941176¢

If you bought 6 gumdrops and 6 chocolate bars you would get 44.411764705882352941176470588242¢ back in change.

Their expected answer:

ANSWER: 46¢ (A chocolate bar costs 7¢; a gumdrop costs 2¢.)

Hmph.  They didn't say anything about rounding to the nearest cent in the original problem.

Comments

[dakhun.livejournal.com]

You won't get any change, because any store that sells chocolate bars for only 7¢ and then rips you off by 2¢ whenever you make a 68¢ purchase is not going to be in business much longer. ;-)

You could buy seven gumdrops for the price of two chocolate bars.

Actually, to be nitpicky, this does not imply that 7g=2c, because they don't say "exactly seven", and they don't say you would have to pay the same amount, nor do they say you won't get change. They just say "you could buy ... for".
What it means is that two chocolate bars cost at least as much as what 7 gum drops costs, but presumably (though not necessarily) less than what 8 gum drops would cost.