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Maths GCSE question

I don't understand how to solve this:


8^5 = 2^2m+3

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Original post by Flammae
I don't understand how to solve this:


8^5 = 2^2m+3


m=6:

You can do this using logs.
NOTE: log is the log to the base 10.

8^5 = 2^2m+3
32768 = 2^2m+3
Log32768 = log2^2m+3
4.515449935 = 2m+3(log2)
2m+3 = (4.51544935/log2)
2m+3 = 15
2m = 12
m = 6


Posted from TSR Mobile
Considering logs are not on any maths GCSE syllabus I thought i'd provide an easier solution:

You know that 2^3=8
Therefore you can change 8^5 to (2^3)^5 = 2^15
therefore 2^15 = 2^2m+3
Therefore 2m + 3 = 15
2m = 12
m = 6

:smile:
Original post by Martins1
Considering logs are not on any maths GCSE syllabus I thought i'd provide an easier solution:

You know that 2^3=8
Therefore you can change 8^5 to (2^3)^5 = 2^15
therefore 2^15 = 2^2m+3
Therefore 2m + 3 = 15
2m = 12
m = 6

:smile:


Yeah sorry it's just the easiest way I thought to do it. I didn't really know how to do it any other way lol. Yeah I never would have thought to change 8 to 2^3 so I just did it using logs.


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Pretty easy question but im surprised its in GCSE. Just make the base number the same then equate the powers
I didn't do GCSEs I did Scottish national 5's last year and highers this year.


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Original post by RossB1702
Yeah sorry it's just the easiest way I thought to do it. I didn't really know how to do it any other way lol. Yeah I never would have thought to change 8 to 2^3 so I just did it using logs.


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There's nothing wrong with it, it's just unlikely to be understood by a gcse student and may not gain the working marks.

The trick with the surds, standard form and indices questions is just to find common looking ones and to manipulate their forms - so in this case to turn both indices into having the same big number. They do these sorts of things because othererwise students just plug figures into their calculators.
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Avatar for David.F
David.F
I got 159 marks, do u think thats enough for an A*
Original post by Martins1
There's nothing wrong with it, it's just unlikely to be understood by a gcse student and may not gain the working marks.

The trick with the surds, standard form and indices questions is just to find common looking ones and to manipulate their forms - so in this case to turn both indices into having the same big number. They do these sorts of things because othererwise students just plug figures into their calculators.


Have you learned logs at your school ? What level are you studying at ?


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Original post by David.F
I got 159 marks, do u think thats enough for an A*


What's it out of ? It really depends on how the paper was for the grade boundary decisions. If the paper was hard then the grade boundaries will be lowered.


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Original post by BirdIsWord
Pretty easy question but im surprised its in GCSE. Just make the base number the same then equate the powers


I believe this is in the IGCSE specification.
Original post by David.F
I got 159 marks, do u think thats enough for an A*


Im in the same boat as you - i think i got around 160 and the grade boundaries for an A* ranges between 150-170 so idk...I hope you do get an A*
Original post by hafsa473
Im in the same boat as you - i think i got around 160 and the grade boundaries for an A* ranges between 150-170 so idk...I hope you do get an A*


150 for an A* is VERY low, It usually averages around 163-165
Original post by 34908seikj
150 for an A* is VERY low, It usually averages around 163-165


last year it was 155 tho
Original post by hafsa473
last year it was 155 tho


Yes, that was the lowest it's ever been. IIRC
Original post by 34908seikj
Yes, that was the lowest it's ever been. IIRC


Oh k then I have a slim chance of getting an A*...:frown:
Original post by hafsa473
Oh k then I have a slim chance of getting an A*...:frown:


Is an A* important ? Like isn't an A an A.
In my exams an A band 1 is just the same as an A band 2.


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Original post by RossB1702
Is an A* important ? Like isn't an A an A.
In my exams an A band 1 is just the same as an A band 2.


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An A* is better than an A and I hope to take maths for A levels - its also the GCSE I'm actually hoping to get an A* in
Original post by hafsa473
An A* is better than an A and I hope to take maths for A levels - its also the GCSE I'm actually hoping to get an A* in


I wouldn't be too hung over it tbh, an A is an A in my opinion. Don't know why you feel the need to stress over not getting an A*.


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Original post by RossB1702
Have you learned logs at your school ? What level are you studying at ?


Haha, no we haven't. I'm at GCSE level and am finally free of maths. Dropping it for any further education! :smile:

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