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

[shockwave77598.livejournal.com]

Lessee.

8y + 6x = 70.
2y=7x, y = 7/2x
28x + 6x = 70. x=2.05882353 cents per gumdrop

each candybar = 7.20588235 cents

6 candybars = 43.2352941
6 gumdrops = 12.3529412
sum= 55.5882353

Change for a dollar = 44cents. (frac pennies are lost)

(checks answer)

Hmph! Rounding to nearest penny - they've obviously never seen a gas pump or a credit card statement...