Stoopid division question I SHOULD understand but don't.

[ulrichburke]

Dear Anyone.

OK, I know I should 'get' this, but I've just been suckered by a YouTube vid and it hurts!

The vid. asked 'Divide 30 by half and add 10.' So I put 25. And it said the answer was 70.

So I got Windows Calculator and entered 30/0.5 and got 60, not 15. And I'm flat not seeing it.

How the *bleep* is half of 30 60!?! I mean you're dividing, so you've gotta end up with a smaller number because you're dividing the original number. So why is Windows Calculator coming up with 60?

What's sad is I've got 3 maths exam qualifications and I'm STILL not seeing this!

Chris.

 

[Deleted member 4993]

Dear Anyone.

OK, I know I should 'get' this, but I've just been suckered by a YouTube vid and it hurts!

The vid. asked 'Divide 30 by half and add 10.' So I put 25. And it said the answer was 70.

So I got Windows Calculator and entered 30/0.5 and got 60, not 15. And I'm flat not seeing it.

How the *bleep* is half of 30 60!?! I mean you're dividing, so you've gotta end up with a smaller number because you're dividing the original number. So why is Windows Calculator coming up with 60?

What's sad is I've got 3 maths exam qualifications and I'm STILL not seeing this!

Chris.

Okay:

This is not a mathematical proof - but -

How much is 60 divided by 12 (= 60/12)? ........ 5

How much is 60 divided by 10 (= 60/10)? ........ 6

How much is 60 divided by 6 (= 60/6)? ........ 10

How much is 60 divided by 5 (= 60/5)? ........ 12

Do you see that as the divisor (the number you are dividing by) increases - the quotient (the result) decreases. So now:

How much is 60 divided by 1 (= 60/1)? ........ 60

How much is 60 divided by ½ [= 60/(½)]? ........ X = ????

You know ½ is smaller than 1 → so by example above X should be greater than 60

 

[Harry_the_cat]

Dear Anyone.

OK, I know I should 'get' this, but I've just been suckered by a YouTube vid and it hurts!

The vid. asked 'Divide 30 by half and add 10.' So I put 25. And it said the answer was 70.

So I got Windows Calculator and entered 30/0.5 and got 60, not 15. And I'm flat not seeing it.

How the *bleep* is half of 30 60!?! I mean you're dividing, so you've gotta end up with a smaller number because you're dividing the original number. So why is Windows Calculator coming up with 60?

What's sad is I've got 3 maths exam qualifications and I'm STILL not seeing this!

Chris.

If you've got 30 pizzas, and each person gets 3 pizzas, how many people can you feed? 30/3 = 10 ... right?

If you've got 30 pizzas, and each person gets 1/2 a pizza, how many people can you feed? 30 / (1/2) = 60...right?

 

[stapel]

OK, I know I should 'get' this, but I've just been suckered by a YouTube vid and it hurts!

The vid. asked 'Divide 30 by half and add 10.' So I put 25. And it said the answer was 70.

So I got Windows Calculator and entered 30/0.5 and got 60, not 15. And I'm flat not seeing it.

How the *bleep* is half of 30 60?

It isn't. But you weren't asked to "find half of thirty", which means "multiply thirty by one-half"; you were asked to "divide thirty by one-half". "Divide in half" (multiply by one-half) is not the same as "divide by one-half" (divide by one-half).

It would be extremely odd if multiplying thirty by one-half gave the same result as dividing it by one-half, don't you think?

 

[Vanice]

The real division

Dear Anyone.

OK, I know I should 'get' this, but I've just been suckered by a YouTube vid and it hurts!

The vid. asked 'Divide 30 by half and add 10.' So I put 25. And it said the answer was 70.

So I got Windows Calculator and entered 30/0.5 and got 60, not 15. And I'm flat not seeing it.

How the *bleep* is half of 30 60!?! I mean you're dividing, so you've gotta end up with a smaller number because you're dividing the original number. So why is Windows Calculator coming up with 60?

What's sad is I've got 3 maths exam qualifications and I'm STILL not seeing this!

Chris.

30 / 0.5 = N

___
.5 l 30

Move the decimal point to the right

60
____
5 l 300

That's how