Bidmas (brackets; indices; divide/multiply; add/subtract)

[Cliff Hanley]

I've just come across an example of this on the following website; http://www.bbc.co.uk/education/guides/zqn3r82/revision/5

The example was;

[40 - (2+4^2)] x 2

The site said that if there are two sets of brackets calculate the inside brackets first. I proceeded as follows;

inside brackets; 2+4^2 = 2+ 4x4 = 2+16 = 18

then the outer brackets; 40 - 18 = 22

then the last part; 22 x 2 = 44

But the site gave 8 as the answer. Any idea where I'm going wrong?

 

[Mark44]

I've just come across an example of this on the following website; http://www.bbc.co.uk/education/guides/zqn3r82/revision/5

The example was;

[40 - (2+4^2)] x 2

The site said that if there are two sets of brackets calculate the inside brackets first. I proceeded as follows;

inside brackets; 2+4^2 = 2+ 4x4 = 2+16 = 18

then the outer brackets; 40 - 18 = 22

then the last part; 22 x 2 = 44

But the site gave 8 as the answer. Any idea where I'm going wrong?

The site is wrong.
In the first step, they have [40 - 6²] * 2. Here they have done the addition before dealing with the exponent. 2 + 4² = 2 + 16 = 18. Addition is at a lower precedence than exponents. At the site, they are evaluating the expression as if it were (2 + 4)² rather than 2 + 4² as given in the problem.

 

[Cliff Hanley]

The site is wrong.
In the first step, they have [40 - 6²] * 2. Here they have done the addition before dealing with the exponent. 2 + 4² = 2 + 16 = 18. Addition is at a lower precedence than exponents. At the site, they are evaluating the expression as if it were (2 + 4)² rather than 2 + 4² as given in the problem.

Thank you. So is my answer of 44 (and the route taken to get there) correct?

 

[Mark44]

Thank you. So is my answer of 44 (and the route taken to get there) correct?

Yes.

 

[SteamKing]

The media is almost invariably horrible at dealing with things mathematical or even requiring the simplest facility in doing computations.

 

[SteamKing]

I've just come across an example of this on the following website; http://www.bbc.co.uk/education/guides/zqn3r82/revision/5

The example was;

[40 - (2+4^2)] x 2

The site said that if there are two sets of brackets calculate the inside brackets first. I proceeded as follows;

inside brackets; 2+4^2 = 2+ 4x4 = 2+16 = 18

then the outer brackets; 40 - 18 = 22

then the last part; 22 x 2 = 44

But the site gave 8 as the answer. Any idea where I'm going wrong?

The Beeb (or the Boob, in this case) evaluated (2+4²) as if it were (2+4)², which leads to the erroneous answer of 8.

 

[Mark44]

The Beeb (or the Boob, in this case) evaluated (2+4²) as if it were (2+4)², which leads to the erroneous answer of 8.

What I said in post 2:

At the site, they are evaluating the expression as if it were (2 + 4)² rather than 2 + 4² as given in the problem.

 

[SteamKing]

What I said in post 2:

Yep, Mark, yer right. I overlooked your post.

 

[Cliff Hanley]

Yes.

Thanks.