[Kroy]

beh... can't believe i missed the first one. more questions!

[MCMLXXXIX]

Originally Posted by southlight

Assuming x is the price of the ball and y the price of the bat. So, "A bat and a ball cost $1.10 in total" means:

x + y = $ 1.10

"The bat costs $1 more than the ball" translates to

y (price of ball) = x + $1

Hence we can say:

x + (x + $ 1) = $ 1.10
2x + $ 1 = $ 1.10
2x = $ 1.10 - $ 1
2x = $ 0.10
x = $ 0.10 / 2
x = $ 0.05

I must be really bored right now. 90 minutes to go until the Apple keynote...


Best regards,
south

thanks for the math lol, i get it now

Originally Posted by Kensta335

You were probably thinking the bat was $1 and the ball .10 cents am I right?

lol yup but i knew it was wrong, thatd be too easy

[JME]

Originally Posted by knext21

You have great memory

Not really, just questions like that are pretty memorable when you ask your mother the same question when you get home, and she calls the school to complain about promoting smoking in school.

I really do like questions like that because it forces students to think things through. I wish more kids would be asked questions like during their primary and secondary education, so they were not still clueless by the time they are taking my class.

[jaiman]

Originally Posted by Suareezay

When researchers put the following three problems to 3400 students in the US, only 17 per cent got all three right. Can you do any better?

1) A bat and a ball cost $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?

2) If it takes five machines 5 minutes to make five widgets, how long would it take 100 machines to make 100 widgets?

3) In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of it?

1) $.05
2) 5 minutes
3) 47 days.

I like all 3 of these questions as you solve each of them in a different way.

I got asked in a recent job interview what 1/7 is to 100 decimal places, no caculator allowed. Actually managed to do it in my head.

[MTV]

Originally Posted by southlight

7 is my guess. 36 butts let you roll 6 cigarettes. Smoke these 6 and you can make another cigarette out of these 6 butts.


Best regards,
south

7 was the answer

Thanks southlight !

[Ron1n]

Originally Posted by Suareezay

When researchers put the following three problems to 3400 students in the US, only 17 per cent got all three right. Can you do any better?

1) A bat and a ball cost $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?

2) If it takes five machines 5 minutes to make five widgets, how long would it take 100 machines to make 100 widgets?

3) In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of it?

I'm surprised. These actually aren't all that hard at all. The cigarette question was harder, imo.

[oldaccount]

Originally Posted by jaiman

1) $.05
2) 5 minutes
3) 47 days.

I like all 3 of these questions as you solve each of them in a different way.

I got asked in a recent job interview what 1/7 is to 100 decimal places, no caculator allowed. Actually managed to do it in my head.

details

[southlight]

Originally Posted by MTV

7 was the answer

Thanks southlight !

My pleasure!


Best regards,
south

[jaiman]

Originally Posted by Suareezay

details

Long division and the sequence repeats after 6 places.

[oldaccount]

yea i saw the sequence repeat, but in your head? fuck.

[radix]

Originally Posted by Suareezay

yea i saw the sequence repeat, but in your head? fuck.

It's not hard once you remember 1/7 is the same as 100/7 with a two decimal place shift.

100 / 7 = 14 remainder 2
200 / 7 = 28 remainder 4
400 / 7 = 57 remainder 1

100 / 7 = 14 remainder 2
200 / 7 = 28 remainder 4

and at this point you should figure out it repeats.

EDIT: Oh yeah, the answer is obviously .142857 repeating.

[jaiman]

Originally Posted by radix

It's not hard once you remember 1/7 is the same as 100/7 with a two decimal place shift.

100 / 7 = 14 remainder 2
200 / 7 = 28 remainder 4
400 / 7 = 57 remainder 1

100 / 7 = 14 remainder 2
200 / 7 = 28 remainder 4

and at this point you should figure out it repeats.

EDIT: Oh yeah, the answer is obviously .142857 repeating.

haha, its funny, I actually find your way harder! In mine I only need to multiply single digits. That's why I like these sorts of problems, there's different ways to solve them.

[jaiman]

Originally Posted by radix

I have another shortcut that I didn't mention because I didn't want to get too complicated in my explanation. I didn't actually divide 7 into 100, 200, or 400 for that matter. I did it in my head by finding the closest large divisor of 100 that is a multiple of 7. In this case 7 * 7 = 49, or 7^2, however you want to look at it.


100 / 49 = 2 remainder 2
then 2 * 7 = 14 so obviously 100 / 7 = 14 remainder 2.

Dividing 200, 400 etc, by 49 is much easier than 7. Although, actually going from 100 to 200 I just doubled the results because the remainder would still be less than 7. But your right about one thing, I didn't divide, I multiplied. It's much easier to think of division as reverse multiplication when doing it in your head.

I hope this makes sense.

I like it!

[radix]

Originally Posted by jaiman

haha, its funny, I actually find your way harder! In mine I only need to multiply single digits. That's why I like these sorts of problems, there's different ways to solve them.

I have another shortcut that I didn't mention because I didn't want to get too complicated in my explanation. I didn't actually divide 7 into 100, 200, or 400 for that matter. I did it in my head by finding the closest large divisor of 100 that is a multiple of 7. In this case 7 * 7 = 49, or 7^2, however you want to look at it. In your head it's much easier to divide 100 by 50 then subtract 2, than it is to just divide 100 by 7 IMO.


100 / 49 = 2 remainder 2
then 2 * 7 = 14 so obviously 100 / 7 = 14 remainder 2.

Dividing 200, 400 etc, by 49 is much easier than 7. Although, actually going from 100 to 200 I just doubled the results because the remainder would still be less than 7. But your right about one thing, I didn't divide, I multiplied. It's much easier to think of division as reverse multiplication when doing it in your head.

I hope this makes sense.

[radix]

Hahaha... editing post deletion failure on my part.

[immiketoo]

Originally Posted by radix

I have another shortcut that I didn't mention because I didn't want to get too complicated in my explanation. I didn't actually divide 7 into 100, 200, or 400 for that matter. I did it in my head by finding the closest large divisor of 100 that is a multiple of 7. In this case 7 * 7 = 49, or 7^2, however you want to look at it. In your head it's much easier to divide 100 by 50 then subtract 2, than it is to just divide 100 by 7 IMO.


100 / 49 = 2 remainder 2
then 2 * 7 = 14 so obviously 100 / 7 = 14 remainder 2.

Dividing 200, 400 etc, by 49 is much easier than 7. Although, actually going from 100 to 200 I just doubled the results because the remainder would still be less than 7. But your right about one thing, I didn't divide, I multiplied. It's much easier to think of division as reverse multiplication when doing it in your head.

I hope this makes sense.

Dear God man, between this thread and the guess the movie thread, I feel really stupid... "So obviously 100/7 = 14 ..." My brain doesn't work this way.

[radix]

Originally Posted by immiketoo

Dear God man, between this thread and the guess the movie thread, I feel really stupid... "So obviously 100/7 = 14 ..." My brain doesn't work this way.

You're not stupid at all, and your brain does work that way, but you have to teach it to. A long time ago I bought a book titled Math Magic (IIRC), it's filled with this sort of shortcut and teaches you to do mental math accurately. Obviously some folks have more aptitude than others. I'm probably mediocre at it. You can learn these little mental tricks, but it does take effort and practice.

[lopealle]

im ust be the only dumbass who didnt get none of these right

[BMW F22]

That's 1/7 is easy. Like someone mentioned I just divided 100/7 and got about .14xx (only goes up to 100th so no need to go any further than that).