Can't make sense of rearranging algebra Watch

grizzly2106
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I have a question regarding rearranging algebra. I have found the soultions for the first part of the question. But am struggling to put it into context when rearranging...Name:  6F34BBC4-B0A2-4263-9C0B-27B43126EE36.jpeg
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On question 3b i keep getting -48, which doesn’t make any sense. I have tried doing all the whatever you do to one side do to the other. But it seems not to work out. I made A the subject of the equation, but keep getting an unrealistic negative number...
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Mr Wednesday
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(Original post by grizzly2106)
I have a question regarding rearranging algebra. I have found the soultions for the first part of the question. But am struggling to put it into context when rearranging...
Think of equations as a perfectly balanced set of scales. When rearranging, you need to keep them balanced, so whatever you do to one side, you have to do to the other as well. Exactly what to do is where a bit of practice and intuition comes in.
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grizzly2106
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(Original post by Mr Wednesday)
Think of equations as a perfectly balanced set of scales. When rearranging, you need to keep them balanced, so whatever you do to one side, you have to do to the other as well. Exactly what to do is where a bit of practice and intuition comes in.
Thanks...I could do the replacing in question 3a, getting realistic measures for the medicine. The 14yr old got 3.5 and the 30 year old 3.75..Any ideas why I'm gettting a negative age after rearranging?
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Mr Wednesday
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(Original post by grizzly2106)
I have a question regarding rearranging algebra. I have found the soultions for the first part of the question. But am struggling to put it into context when rearranging...
Think of equations as a perfectly balanced set of scales. When rearranging, you need to keep them balanced, so whatever you do to one side, you have to do to the other as well. Exactly what to do is where a bit of practice and intuition comes in.

(Original post by grizzly2106)
Thanks...I could do the replacing in question 3a, getting realistic measures for the medicine. The 14yr old got 3.5 and the 30 year old 3.75..Any ideas why I'm gettting a negative age after rearranging?
Must be a maths error in the rearrangement, I get them all coming out positive and nice sensible looking numbers.

You will sometimes end up with 2 possible solutions for a quadratic equation (which this is not) and you may then have to chose the one that is "physical", e.g. a positive age is ok, a negative age is not. If you get an unphysical answer here, its telling you to look for an error.
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AGrizzlyBearo
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Can you show your workings for the question where you are getting a negative?
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grizzly2106
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(Original post by AGrizzlyBearo)
Can you show your workings for the question where you are getting a negative?
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simon0
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(Original post by grizzly2106)
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It looks like you had three attempts. The lower-left attempt is correct.

In general, be careful not forgetting the "d" as in the other two attempts the "d" (in term 10d) dissapears.
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grizzly2106
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(Original post by simon0)
It looks like you had three attempts. The lower-left attempt is correct.

In general, be careful not forgetting the "d" as in the other two attempts the "d" (in term 10d) dissapears.
That’s great! It works out as 22...much appreciated with your help...it’s so much clearer now!!!
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Mr Wednesday
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(Original post by grizzly2106)
That’s great! It works out as 22...much appreciated with your help...it’s so much clearer now!!!
And congrats for actually showing your workings and getting a fix in the end ! Lots of hopeful seekers after homework answers here just post and run, their loss as they miss out on really useful guidance that way.
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