Math Is Fun Forum

candyxy

Member

Registered: 2011-04-27

Posts: 7

easy question?? 30÷2(2+3)÷5 = ?

Dear all

Please help to solve this qn.. there has been a debate on this simple qn, but of course I already have the answer in mind which I am 99% confident. I just want to know whether my answer is 100% correct by hearing from the experts here.

30÷2(2+3)÷5 = ?

My answer is 15. What about yours?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: easy question?? 30÷2(2+3)÷5 = ?

Hi candyxy;

Change that 99% to 100%.

Welcome to the forum!

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

candyxy

Member

Registered: 2011-04-27

Posts: 7

Re: easy question?? 30÷2(2+3)÷5 = ?

Hi thx for the reply!

hehe can u believe more than 13k ppl voted 0.6 but only 6k ppl voted for 15 on facebook?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: easy question?? 30÷2(2+3)÷5 = ?

Hi candyxy;

Yes, I can. Few people know the order of operations as well you do.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

candyxy

Member

Registered: 2011-04-27

Posts: 7

Re: easy question?? 30÷2(2+3)÷5 = ?

they know the BODMAS rule but they insist that the 2 is attached to the (), which gives them 0.6.. many calculators also show 0.6

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: easy question?? 30÷2(2+3)÷5 = ?

PEMDAS is what I use and I got .6 also.

But Mathematica and Maple the big boys on the block get 15. So either you compute like a whiz or you have access to some slick software!

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

candyxy

Member

Registered: 2011-04-27

Posts: 7

Re: easy question?? 30÷2(2+3)÷5 = ?

lol.. 15 or 0.6?

candyxy

Member

Registered: 2011-04-27

Posts: 7

Re: easy question?? 30÷2(2+3)÷5 = ?

this is my explanation..

the problems we face are alw e.g. 30 - 2*(2+3) / 5, which naturally will be multiplying the 2 to () 1st.. but for this case, it is 30 / 2*(2+3) / 5 so the left to right rule must be followed.. the order of operations only apply to the numbers IN the bracket, not OUTSIDE it, so the 2 cannot be the priority..

as for the calculator, I think most calculators just auto add in brackets for u, so it becomes 30 / [2*(2+5)] / 5 which gives 0.6..

Microsoft excel gives ans 15 hehe

the debate can be never ending.. hehe

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: easy question?? 30÷2(2+3)÷5 = ?

Hi;

You successfully stumped the m, in a computation problem no less. My hat is off to you, if I had a hat. Or if I could remember where it was.

Anyway, I could not disagree more with this statement.

the order of operations only apply to the numbers IN the bracket, not OUTSIDE it

Now that you tell me that a Microsoft product got 15, I will go to my death saying the answer is anything but 15.

All kidding aside I see that the answer is 15 and you are correct!

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

candyxy

Member

Registered: 2011-04-27

Posts: 7

Re: easy question?? 30÷2(2+3)÷5 = ?

yay hehe thx a lot for supporting my answer!

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: easy question?? 30÷2(2+3)÷5 = ?

hi

I think it is 15 too.

I didn't use any software; just my brain!

30 ÷ (2*(2+3)) ÷ 5 = 0.6

In the absence of the extra bracket you should do the first divide (15) then multiply by the result of doing the bracket (75) and finally divide again (15).

Bob

Last edited by Bob (2011-04-27 19:35:18)

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: easy question?? 30÷2(2+3)÷5 = ?

Yes, for anyone else looking at this

Do the parentheses first:

Now everything has the same precedence so start from the left.

30 / 2 = 15

15 * 5 = 75

15

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: easy question?? 30÷2(2+3)÷5 = ?

Oh bobbym, you just pre-posted my edit.

Bob

ps hi candyxy

many calculators also show 0.6

which ones?

Last edited by Bob (2011-04-27 19:39:55)

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: easy question?? 30÷2(2+3)÷5 = ?

Are you saying my post is pre-posterous?

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

candyxy

Member

Registered: 2011-04-27

Posts: 7

Re: easy question?? 30÷2(2+3)÷5 = ?

u try on ur calculator.. 30÷2(2+3)÷5 and also try 30÷2x(2+3)÷5

both give different answer.. it's not the calculator's error, it's just for most calculators, they'll add in an extra bracket for u which makes it 30÷[2(2+3)]÷5.

yeah this kinda question doesn't need any device to get the ans, we just want to cross check.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: easy question?? 30÷2(2+3)÷5 = ?

hi candyxy and bobbym

b: I wouldn't dream of such a thing.  I think I may have tortured the English language somewhat.  It was a 'kind of' pun.

'post' meaning a message in a thread OR coming after as in 'post meridian'

'pre' meaning before as in 'prefix'. 

Overall = you got your post in while I was typing mine.

c:  I have two calculators but both are so old they are steam driven.  Neither will accept input where the multiplication sign has been left out.  I consider that a benefit since it stops the machine from 'assuming' what you meant.  Tell your friends they shouldn't believe every answer they get from a calculator.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: easy question?? 30÷2(2+3)÷5 = ?

Hi Bob;

I know, I just could not resist the pre-posterous-ness of it all.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.