Understanding 20 ÷ 2(1+1)= ? - Homework Help

[quietrain]

Homework Statement

what is 20 ÷ 2(1+1)= ?

The Attempt at a Solution

is it 20 ÷ 2 x (2) = 10 x (2) = 20?

or 20 ÷ 2(2) = 20 ÷ 4 = 5 ?

 

[eumyang]

There have been some threads elsewhere dealing with this type of question. Take a look at
https://www.physicsforums.com/showthread.php?t=488334", for instance.

 

[quietrain]

ah thank you , will give it a look

 

[symbolipoint]

Your first way, giving 20, is correct, although the best way to write the expression is not with that kind of Division operation symbol. I would prefer to write it this way, if you could go from text display into proper typesetting yourself:

(20/2)*(1+1)

The first Division is done first, and the result is multiplied by "one plus one". (That also means that the original shown expression in the grouping symbols, "1+1" would be done before doing the first Division).

 

[quietrain]

Your first way, giving 20, is correct, although the best way to write the expression is not with that kind of Division operation symbol. I would prefer to write it this way, if you could go from text display into proper typesetting yourself:

(20/2)*(1+1)

The first Division is done first, and the result is multiplied by "one plus one". (That also means that the original shown expression in the grouping symbols, "1+1" would be done before doing the first Division).

hmm but shouldn't the 2 be a like a factor of (1+1)?

so by right it should be seen as 20 ÷ [2(1+1)] = 5

thats the reason why we write it as 2(1+1) and not 2 x (1+1) right? although i admit it is a shorthand notation

 

[Borek]

It was beaten to death, please refer to the old thread. Math is clear here, notation pretends to be ambiguous.

Topic locked.