### Brain Teasers

# The Hardware Store

A man goes into a hardware store to purchase some knobs. To purchase one knob you must pay a minimum of 4 U.S. coins. Two knobs can be purchased with a minimum of 6 U.S. coins. 3 knobs require a minimum of 2 U.S. coins. How much does one knob cost?

U.S Coins include: a penny ($.01), a nickel ($.05), a dime ($.10), a quarter ($.25), a half-dollar ($.50), and a silver dollar ($1.00).

U.S Coins include: a penny ($.01), a nickel ($.05), a dime ($.10), a quarter ($.25), a half-dollar ($.50), and a silver dollar ($1.00).

### Hint

Three knobs cannot be purchased with $0.50.### Answer

One knob costs $0.17Hide Hint Show Hint Hide Answer Show Answer

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## Comments

It would have been cool to have more to the answer than , well, just the answer. Why not tell how much the others cost, or explain how to figure it out?

Ne Comprende senior

Err... well if one cost $0.17, the others cost $0.34 and $0.51 respectively (since it was the cost of one, two and then three knobs).

17Â¢ is: One dime, one nickel, and two pennies (four coins)

34Â¢ is: One quarter, one dime, and four pennies (six coins)

51Â¢ is: One half dollar, one penny (two coins).

I'd be interested to know if there was another way to figure it out, besides plugging in. Personally, it took me about two full minutes before the number 51 popped into my head, which i know is divisible by 3 and 17. Then I checked the coins and it worked.

if there's some algebraic way to set this up and solve, I'd be very interested.

17Â¢ is: One dime, one nickel, and two pennies (four coins)

34Â¢ is: One quarter, one dime, and four pennies (six coins)

51Â¢ is: One half dollar, one penny (two coins).

I'd be interested to know if there was another way to figure it out, besides plugging in. Personally, it took me about two full minutes before the number 51 popped into my head, which i know is divisible by 3 and 17. Then I checked the coins and it worked.

if there's some algebraic way to set this up and solve, I'd be very interested.

haha... it took a couple times to get it... but i liked it!

how come the answer isnt 25 cents? can it be 25 cents also? no i dont need to explain...ok fine... so the first one ...... 1 dime 3 nickles (4 coins for one knob) , second .....1 quarter, 5 nickles (6 coins for two knobs ) and the thirsd a 5o cent coin and a quarter... am i wrong? did i miss something? if i didnt ...the hint is misleading.. forcing you into one conclusion... if my math is wrong you can make fun of me

interesting

I'm glad that most of u liked my teaser.

Jan 02, 2005

If the answer was 25 cents, then 1 knob could be purchased with a minimum of one coin...which would be a quarter. Not 6 coins.

y'all have better math skills than I do! LOL dont think I could have figured that one out ! LOL

All I know is 2+2=4 and 1+1=2

and 2pir is how you get the circumference of a circle. My geometry is better than that kind of math

and 2pir is how you get the circumference of a circle. My geometry is better than that kind of math

"Your" geometry?

it could also be a dollar...that's the answer i got...

One Knob: 4 Coins = 4 quarters.

Two Knobs: 6 Coins = 4 quarters and two half dollars.

three knobs: 2 Coins = 2 silver dollars.

right?

One Knob: 4 Coins = 4 quarters.

Two Knobs: 6 Coins = 4 quarters and two half dollars.

three knobs: 2 Coins = 2 silver dollars.

right?

Oh wait...I just caught my own mistake...math never was my strong suit, i suppose

Notice the word MINIMUM in the body of the teaser. MINIMUM.

aargh!! i didnt feel like working this out!! im so lazy

It took me a couple of minutes to figure it out.

Omega, I was thinking the same thing. The only way I could figure this out is assigning some values to three knobs, and then going from there. And you made a mistake but 1 quarter, 1 dime, and 4 pennies is 39 cents. I believe you meant a nickel. (I know it's just a misprint, but I thought I'd point it out).

Start by thinking of combinations of two coins (for the three knobs) and work out the sum: two pennies = 2, penny and a dime = 11 etc. To be a possible combination the sum must be divisible by 3. This gives you the possible cost of the knob. e.g penny plus a nickel = 6 which is divisible by 3, but 2 cents can't be made from 4 coins so is discounted as an answer. The answer pops out very quickly.

I'd have to contest this one :

1 knob could be 4 quarters

2 could be 4dimes and 2 nickels

3 could be 2 half dollars

Thus making each knob $1

Which sounds more realistic in todays market!

1 knob could be 4 quarters

2 could be 4dimes and 2 nickels

3 could be 2 half dollars

Thus making each knob $1

Which sounds more realistic in todays market!

I forgot to mention that TWO knobs fall under the BUY ONE GET ONE FREE promotion!

It's just Monday morning it's to early in the week for me to take on this one. But it was a challenge. Somebody put on a pot of coffee

not clear at all doesnt say not to use same coin 1.50is a good answer also

IM NOT SO GOOD AT MATH

ITS EVIL

ITS EVIL

Actually, $1.50 doesn't work, as one knob uses a MINUMUM of 4 coins. You can get to 1.50 with 3 50 cent pieces.

Math problems aren't brain teasers.

for some strange reason, i was thinking at first that all the coins had to be the same (like three nickels, or whatever...) fun, just the same!

wait...i guess that would have to be four nickels, since "a minimum of three U.S. coins" wasn't one of the options! OOPs!

I tried the problem and I got $0.67 for one knob.

the teaser does not say that one has to pay the exact amount. i found this confusing since i had assumed that was not a requirement.

as an example, if the knob cost $.17 then purchasing two would only require 2 coins - the quarter and dime.

as an example, if the knob cost $.17 then purchasing two would only require 2 coins - the quarter and dime.

i think it can also be .20

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