You are Here: Home >< Maths

# Rearranging a formula Watch

1. For the formula:

I have to make a the subject. What is the right answer? Please explain HOW you get the correct answer with working out. Thanks.

I got:
a=8-4c
44-----
444b-c

But I got the wrong answer
2. (Original post by krisshP)
For the formula:

I have to make a the subject. What is the right answer? Please explain HOW you get the correct answer with working out. Thanks.

I got:
a=8-4c
44-----
444b-c

But I got the wrong answer
Its not allowed to post full solutions.

Can you show your working, then i can tell you where you went wrong.
3. (Original post by krisshP)
For the formula:

I have to make a the subject. What is the right answer? Please explain HOW you get the correct answer with working out. Thanks.

I got:
a=8-4c
44-----
444b-c

But I got the wrong answer
You forgot to multiply ab by 4 when getting rid of the fraction.
4. when multiplying ab by 4 I get a wrong answer of

8-4c
-------=a
4b-c

Here I first multiplied by 4 and expanded to get:
4ab-ca+4c=8
Then I -4c to get:
4ab-ca=8-4c
After this I factorised the LHS to get:
a(4b-c)=8-4c
Then I divided both sides by (4b-c) to get the answer stated above.

WHY did I fail?
5. (Original post by krisshP)
when multiplying ab by 4 I get a wrong answer of

8-4c
-------=a
4b-c

Here I first multiplied by 4 and expanded to get:
4ab-ca+4c=8
Then I -4c to get:
4ab-ca=8-4c
After this I factorised the LHS to get:
a(4b-c)=8-4c
Then I divided both sides by (4b-c) to get the answer stated above.

WHY did I fail?
What is the final answer supposed to be?
6. (Original post by krisshP)
when multiplying ab by 4 I get a wrong answer of

8-4c
-------=a
4b-c

Here I first multiplied by 4 and expanded to get:
4ab-ca+4c=8
Then I -4c to get:
4ab-ca=8-4c
After this I factorised the LHS to get:
a(4b-c)=8-4c
Then I divided both sides by (4b-c) to get the answer stated above.

WHY did I fail?

Multiply throughout by 4,
7. Not sure but I know that the answer of:

8-4c
------ = a
4b-c

is wrong.

What answer do you get? Is it the same as if it is it could mean that mymaths is wrong.
8. (Original post by krisshP)
Not sure but I know that the answer of:

8-4c
------ = a
4b-c

is wrong.

What answer do you get? Is it the same as if it is it could mean that mymaths is wrong.
I have indicated your mistake in my previous post.
9. Thanks Raheem94 for making me learn from a mistake
10. (Original post by krisshP)
Thanks Raheem94 for making me learn from a mistake
You are welcome.

By the way, what answer do you get, so that i can confirm if you are right or wrong.
11. I entered the new answer on mymaths and I got a tick, so the new answer was correct
Thanks

Updated: April 2, 2012
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### Stuck for things to do this summer?

Come and get some inspiration.

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.
{"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0}