Friday, February 8, 2013

The Question that 50% of the Harvard, Princeton and MIT students get wrong but you will solve.

This question is present in the century-old math books and is usually marked for the elementary school age.  Yet it is the question that get many adults confused. A question that one may fear to get on a job interview or an IQ test. A question where your tongue will compete with your logic. Where answering fast usually means answering wrong. Rumor goes around Facebook and email that 50% of the Harvard, Princeton and MIT students get the answer wrong.  But you surely can do this right:


At a candy store a gum and a candy cost $1.10.
Gum costs one dollar more than the candy.
How much does the candy cost?

Image by Bart Heird, distributed under CCL.

Your answers accepted any time until midnight on Sunday on our Family Puzzle Marathon. They will be hidden till then and everyone who submitted something reasonable will get a puzzle point.

33 comments:

Anonymous said...

The candy costs $0.05.
(The gum costs $1.05, $1 more).

TracyZ

renee said...

My second-grader and I both got it, but my fourth-grader did not: the candy is 5 cents and the gum is $1.05. And my husband actually came up with a formula (subtract a dollar from the total and divide the result by 2), while the kid and I just kind of noodled it out. Happy snow day!

2boyzMarks4 said...

The candy costs 5 cents.

2boyzMarks4 said...

the candy costs 5 cents.

Andrée said...

candy $.05 gum $1.05

SteveGoodman18 said...

The candy costs 5 cents. I refuse to believe that 50% of top college students get this wrong! If gum is one dollar more than the candy then the gum is $1.05 and the candy $0.05 for a total of $1.10.

Of course, if you change the punctuation to "Gum costs one dollar, more than the candy," then the gum could cost $1 and the candy 10 cents.

Annie said...

The gum cost $1.05 and the candy costs $.05. Combined they cost $1.10 and the gum cost $1.00 more than the candy

Katrina said...

The candy costs $0.05.

TyYann said...

The candy costs $0.05.

Jerome said...

Let the Candy Cost x
Let the gum cost x + 1
Total Cost 1.10

x + x + 1 = 1.1
2x + 1 = 1.1
2x = 0.1
x = 0.05

Candy = 0.05
Gum = 1.05 Hence the gum is 1 dollar more than the candy.

Leah said...

Gum is $1.05, candy is $0.05

Jerome said...

Here is a reference to a collection of riddles that I scored really poorly on. I got 3 right on the first set and 6 right on the second.

http://www.berro.com/entertainment/riddles.htm

anne-marie said...

Let x= the cost of one piece of candy
We have (1+x)+x = 1.10
Associative and Communicative properties of addition
1+2x= 1.10 so 2x= 0.10 and x= $0.05

Heidi B said...

Candy - $.05
Gum- $1.05
Total- $1.10

Thanks for the friday fun. Even if I don't get around to submitting an answer, it's always fun to think through your puzzles!

Susan said...

Candy = $0.05
Gum = 1.05
Total = $1.10

That's either really cheap candy, or really expensive gum!

Lynnet said...

Candy costs $0.05.

I figured this out very quickly in my head, but here's a mathematical way of looking at it.

x=gum, y=candy

x+y=1.10
+ x-y=1.00
------------
2x=2.10
x=1.05

So now we know that gum costs $1.05, but that's not what we are actually looking for.

x+y=1.10
1.05+y=1.10
y=.05

The final answer: Candy costs $0.05.

I also had my younger brother look at this, and took him through a basic way of solving it, whereupon he figured out the answer.

Mai B. said...

The gum costs $1.05 and the candy is $0.05, for a total cost of $1.10 for the gum and candy.

Anonymous said...

I think the candy cost $.10 or ten cents since the candy and gum together cost $1.10 so $1.00 less than $1.10 is $.10.


Gurubandhu

jerome's wife said...

The candy costs .05 cents, I figured this out while eating a sub at the Subway. If the gum costs $1.00 more than the candy, and gum and candy together total $1.10, then I figured that the word "more" was the important factor, and the question is not saying that the gum costs $1.00, but that the gum was $1.00 more than the candy. So to get a total of $1.10 for both gum and candy, I would have to add .05 cents to the gum and the remainder would then be .05 for the candy. This was hard to explain and I'm not sure if I did.

Anonymous said...

The answer is
candy is 5 cents
(1.05 + 0.05 is 1.10)

I slowed my self to think for a few seconds rather than answer it immediately, which would have been wrong, so maybe this is a test of impulsivity!

Gorica (via email)

Natalie said...

10 cents.

There's a trick, isn't there?

Rosalyn said...

The candy costs 5 cents.

Patricio said...

5 c.

Anonymous said...

Candy is 5 cents!

annicita said...

Candy costs $0.05, gum costs $1.05

annicita said...

Candy costs $0.05 and gum costs $1.05.

Claudio Meller said...

A candy cost 0.05

Sandy said...

Candy is $0.05
Gum is $1.05
The difference is $1.00.
The sum is $1.10.

g+c = 1.10
g-c = 1.00
g = 1.05
c = 0.05

T.J. said...

X + (X + 1.00) = 1.10
2x = .10
x = .05

The candy costs 5 cents and the gum costs $1.05

Maria said...

So many correct answers! I need to be careful to give you each a puzzle point.

Let's admit that it seems easy after you spend a few min thinking about it but the first impulsive answer we all had was $1 for gum and $0.1 for candy. In a fast Q&A interview we all are very likely to shoot this answer out.

But then when you think about it and check $1-$0.1 = $0.9 but the gum should be $1 more than the candy.

Candy costs something.
Gum costs this something, plus a $1.
Together, they are 2 times something + $1 = $1.1
2 times something = $0.1
something = $0.05 = 5 cents

candy is 5 cents
gum $1 + 5 cents

Enjoy the winter and see you back next week!

Anonymous said...

I think I was the only one to get it wrong and I did not even go to an Ivy League school.

Gurubandhu

Anonymous said...

I'm 9 years old and I know it. Candy costs 5 cents. Gum is 1 dollar 5 cents! Just have to think. This might be awkward if my answer is wrong, but it's right, actually! And I didn't even look at the comments. At first I thought the candy was 10 cents but it's actually 1 DOLLAR MORE. so it has to be 5 cents. And I'm English so I barely know about dollars and cents. This is the kind of stuff in my textbook, but MUCH harder.

Anonymous said...

Being from one of the aforementioned schools, namely Harvard, I assure you 50% of the students would not get it wrong.

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