Just Indices

Algebra Level 1

4 8 8 = 1 2 8 × 1 6 a \Large 48^8=12^8 \times 16^a

If a a is a positive integer that satisfy the equation above, find the value of a a .


The answer is 4.

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46 solutions

48 8 4 8 = 12 8 \frac{{48}^{8}}{{4}^{8}}={12}^{8}

48 8 12 8 = 4 8 \frac{{48}^{8}}{{12}^{8}}={4}^{8}

4 8 = 16 a {4}^{8}={16}^{a}

4 8 = 16 4 {4}^{8}={16}^{4}

a = 4 a=4

how come that the denominator is 4 ^8 ?

Tiffany Pandes - 6 years, 8 months ago

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48/4=12, 48^2/4^2=12^2 48^3/4^3=12^3...48^8/4^8=12^8 Simple!

Victor Paes Plinio - 6 years, 7 months ago

4^8 = (4^2)^a 4^8 = 4^2a 8 = 2a a = 4

Deano Damario - 6 years, 8 months ago

48^8=12^8 4^4a 48^8=12^8 4^4*2 48^8=48^8

Rahul Kumar - 6 years, 8 months ago

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Why have you posted it two times???

Anuj Shikarkhane - 6 years, 8 months ago

Can u please explain it clearly............. I don't get ur method..........

Siddharth tiwari - 6 years, 6 months ago

48^8=12^8 4^4a; 48^8=12^8 4^4*2 ; 48^8=48^8

Rahul Kumar - 6 years, 8 months ago
Jud Son
Nov 18, 2014

Using laws of exponent, a m × a n = a m + n a^{m} \times a^{n} = a^{m+n}

4 8 8 = 1 2 8 × 4 8 48^{8} = 12^{8} \times 4^{8}

4 8 8 = 1 2 8 × 4 2 × 4 2 × 4 2 × 4 2 48^{8} = 12^{8} \times 4^{2} \times 4^{2} \times 4^{2} \times 4^{2}

4 8 8 = 1 2 8 × 16 × 16 × 16 × 16 48^{8} = 12^{8} \times 16 \times 16 \times 16 \times 16

4 8 8 = 1 2 8 × 1 6 4 48^{8} = 12^{8} \times 16^{4}

Therefore, a a = 4

Sunil Sadat
Nov 2, 2014

48^8 = 12^8 X 16^a

Or, 12^8 X 16^a = 48^8

Or, 16^a = 48^8/12^8

Or, 16^a = 4^8

Or, 2^4.a = 2^2.8

Or, 2^4a = 2^16

Or, 4a = 16

Or, a = 16/4

And Finally, a = 4

Sameen Tz
Oct 7, 2014

488= 128*16a i.e 16a=(48^8)/(12^8) or, log16a=log65536 or, a= (log65536)/(log16) i.e a=4

Sarah Biscuita
Oct 7, 2014

(6^8)(8^8)=(6^8)(2^8) * 16^a

(6^8)(8^8)/(6^8)(2^8) =16^a (8^8)/(2^8)= 16^a

(2^8)(4^8)/(2^8)=16^a

(4^8)=16^a

(4^8)=(4^a)(4^a) a=4

best one dude..

SABYASACHI BANERJEE - 6 years, 8 months ago
Jacqueline Hunter
Jul 29, 2015

48^8 =12^8 x 16^a

48^8/12^8 = 16^a

(48/12)^8 = 16^a

4^8 = 16^a (make bases the same. 4^2 = 16)

4^(2x4) = 16^a

(4^2)^4 = 16^a

16^4 = 16^a

4 = a (yay!)

Rajat Nair
Oct 29, 2014

Good question........................

Ra Sunag
Nov 3, 2015

48^8=12^8*16^a

8log48=8log12+a log16

8log(12*4)=8log12+a log(2^4)

8log12+ 8log 4 = 8 log 12 + 4a log 2

8 log 12 cancels out So, 8 log (2^2) = 4a log2 16 log 2 = 4a log 2

Therefore, a= 16/4=4

Bonnor Sullivan
Jan 16, 2015

8log48 = 8log12 + alog16 (8log48-8log12)/log16 = a = 4

Luciano Canela
Jan 6, 2015

Remembering some properties of potency:

1 -

(a * b) ^n = (a^n) * (b^n)

2 -

a^b^n = a^b*n

Where a, b and n are positive integers

We can use the same reasoning:

(48 ^8)= (12 * 4)^8 = 12^8*4^8

16^a = 4^2^a = 4^2*a

Thus,

48^8 = 12^8 * 16^a

12^8 * 4^8 = 12^8 * 16^a

4^8 = 4^2*a

As the potencies are from same base, so:

8 = 2*a

a = 4

(48 to the power 8)=(12 to the power 8)×(16 to the power a)

(48 to the power 8)÷(12 to the power 8)=(16 to the power a)

(4 to the power 8)=(16 to the power a); (4 to the power 8)=(4 to the power 2a) 2a=8; a=8÷2; a=4.

Jonathan Liem
Dec 5, 2014

4 8 8 = 1 2 8 × 1 6 a 48^{8} = 12^{8} \times 16^{a}

3 8 × 1 6 8 = 3 8 × 4 8 × 1 6 a 3^{8} \times 16^{8} = 3^{8} \times 4^{8} \times 16^{a}

1 6 8 = 4 8 × 1 6 a 16^{8} = 4^{8} \times 16^{a}

4 16 = 4 8 × 4 2 a 4^{16} = 4^{8} \times 4^{2a}

16 = 8 + 2 a 16 = 8 + 2a

8 = 2 a 8 = 2a

a = 4 a = \boxed{4}

Amrithaa Ranjith
Nov 7, 2014

48^8 can b written as 12^8 4^8 n So 12^8 4^8=16^a*12^8 Cancel 12^8 on both sides. 4^8=4^2a 8=2a A=4

Harsh Rathore
Nov 4, 2014

(48)^8=(12x4)^8 =12^8x4^8=12^8x16^4

Vipin Singh
Oct 29, 2014

a= 4

(12X4)^8 = 12^8 X 4^8

4^(2x4) = 16^4

Ariella Lee
Oct 29, 2014

Given:

4 8 8 = 1 2 8 × 1 6 a 48^{8}=12^{8} \times 16^{a}

Divide both sides by 1 2 8 12^{8} .

4 8 8 1 2 8 = 1 2 8 × 1 6 a 1 2 8 \frac{48^{8}}{12^{8}}=\frac{12^{8} \times 16^{a}}{12^{8}}

Simplify.

4 8 8 1 2 8 = 1 6 a \frac{48^{8}}{12^{8}}=16^{a}

Since 12 12 is a factor of 48 48 , write 48 48 as a 12 4 12\cdot4 in order to make it cancel with the denominator.

( 12 4 ) 8 1 2 8 = 1 6 a 1 2 8 4 8 1 2 8 = 1 6 a 4 8 = 1 6 a \frac{(12\cdot4)^{8}}{12^{8}}=16^{a}\\\frac{12^{8}\cdot4^{8}}{12^{8}}=16^{a}\\4^{8}=16^{a}

16 16 can be written as 4 2 4^{2} . Write it as a power of 4 4 so the exponents can be equated.

4 8 = ( 4 2 ) a 4 8 = 4 2 a 8 = 2 a a = 4 4^{8}=(4^{2})^{a}\\4^{8}=4^{2a}\\8=2a\\\boxed{a=4}

Siddhartha Gaba
Oct 28, 2014

48^8 = 12^8 * 16^a 48^8/12^8 = 16^a ( 48/12)^8 = 16^a 4^8 = 16^a 16^a =65536 65536 = 16^4 So, a = 4

Daniel Vallance
Oct 17, 2014

48^8 = 12^8 x (48/12)^8

48/12 = 4

4^8 = 16^(8/2) = 16^4

Alice Milford
Oct 16, 2014

4 8 8 = 12 8 × 16 a 48 8 = ( 2 4 × 3 ) 8 48 8 = 2 32 × 3 8 12 8 × 16 a = ( 2 2 × 3 ) 8 × ( 2 4 ) a 12 8 × 16 a = 2 16 × 3 8 × 2 4 a 12 8 × 16 a = 2 16 + 4 a × 3 8 2 32 × 3 8 = 2 16 + 4 a × 3 8 32 = 16 + 4 a 32 16 = 4 a 16 = 4 a a = 4 48 ^{ 8 }={ 12 }^{ 8 }\times { 16 }^{ a }\\ \\ { 48 }^{ 8 }={ { (2 }^{ 4 }\times 3) }^{ 8 }\\ { 48 }^{ 8 }={ 2 }^{ 32 }\times { 3 }^{ 8 }\\ \\ { 12 }^{ 8 }\times { 16 }^{ a }={ { (2 }^{ 2 }\times 3) }^{ 8 }\times { { (2 }^{ 4 }) }^{ a }\\ { 12 }^{ 8 }\times { 16 }^{ a }={ { 2 }^{ 16 }\times { 3 }^{ 8 } }\times { { 2 }^{ 4a } }\\ { 12 }^{ 8 }\times { 16 }^{ a }={ { 2 }^{ 16+4a }\times { 3 }^{ 8 } }\\ \\ { 2 }^{ 32 }\times { 3 }^{ 8 }={ { 2 }^{ 16+4a }\times { 3 }^{ 8 } }\\ \\ 32=16+4a\\ 32-16=4a\\ 16=4a\\ \boxed{a=4}

Efraim Gunawan
Oct 16, 2014

48^8 = 12^8 x 16^a

(12x4)^8 = 12^8 x (4x4)^a

12^8 x 4^8 = 12^8 x 4^a x 4^a

4^8 = 4^2a

2a= 8

a= 8/2 = 4

Lokos Smiler
Oct 16, 2014

since 48=4*12 than we satisfy 12^8 with 12^8 and we have left 4^8=16^a 16=4^2
4^8=4^2a 2a=8 result a=4

Divide the LHS and RHS by 12^8.Now 4^8 = 16^a => 4^8 = 4^2a => 2a=8 => a=4.

Ramon Lasala
Oct 15, 2014

48^8 = 12^8 x 16^a

Rewrite

(3 x 2^4)^8 = (2^2 x 3)^8 x (2^4)^a

(3^8)(2^32) = (2^16)(3^8)(2^4a)

(3^8)(2^32) = (3^8)(2^(16+4a))

Equate the exponents of 2

32 = 16 + 4a

Solve for a

32 - 16 = 4a

16 = 4a

Divide both sides by 4

4 = a or a = 4

Vortex Monta
Oct 14, 2014

48^8 = 12^8*16^a or, 48^8/12^8 = 16^a or, (48/12)^8 = 16^a or, 4^8 = 4^2a or, 8 = 2a or, a = 4 (Ans)

Razibul Islam
Oct 14, 2014

48^8=12^8 * 16^a
=> (48^8) /(12^8) =16^a
=> {12^(4 8)/12^8}=16^a
=> 4^8=16^a
=> 4^(2

4)=16^a
=> 16^4=16^a
=> 4=a
=>a=4




Ayush Prasad
Oct 14, 2014

Write a solution.

Anisur Anis
Oct 13, 2014

4^16x3^8= 4^8x3^8 +16^a = > 4^8=16^a=4^2a = > 2a=8 = > a=4

Raja Kotha
Oct 13, 2014

48^8=12^8*4^8 4^8=16^4 therefore a=4

Kabir Bagai
Oct 12, 2014

48^8=48^4x16^a ^8=^4x16a 4a=16 a=4

12^8 × 4^8= 12^8×4^a×4^a 4^8=4^2a
8=2a a=4

Anirudha Devadkar
Oct 11, 2014

48=12*4

so 48^8=12^8*(4)^8

but here we want 16^a

so4^8=(4^2)^(8/2)

4^8=16^4

Rahul Chudasama
Oct 11, 2014

48^8 = 12^8 * 16^a --> 48^8/12^8 = 16^a --> (48/12)^8 = 16^a --> 4^8 = 16^a --> 4^8 = 4^2a --> 8 = 2a.........................(If a^m = a^n then m = n) --> a = 4.

Ganesh Rajapkar
Oct 11, 2014

(16^8)/(12^8)=(16^a); 65536=(16^a); a=(log65536)/(log16); a=4

Shivam Salaria
Oct 11, 2014

48^8=12^84^4a=)48^8=12^84^4*2 =)48^8=48^8

Tamal Das
Oct 9, 2014

12*4=48.......so 12^8 *4^8 =48^8. Then 4^8 = 16^a. a=4

You should use LaTeX \LaTeX

Anuj Shikarkhane - 6 years, 8 months ago

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Everyone should.

Micah Wood - 6 years, 7 months ago

48^8=12^8 16^a (12 4)^8=12^8 16^a 12^8 4^8=12^8 16^a divide both sides by 12^8 12^8 4^8/12^8=12^8*16^a/12^8 then, 4^8=16^a express both sides with the same base(we can base it with 2 or 4, i choose 4) 4^8=4^2a equate the exponents, 2a=8 then divide both sides by 2 to get the value of a 2a/2=8/2 so, the value of a is 4....

Deepak Singh
Oct 9, 2014

12 16=192 means 192= 48^4, 12^8 16^8-4 so that 48^8=12^8*16^4

Jack Hall
Oct 8, 2014

4 8 8 = ( ( 4 ) ( 12 ) ) 8 = ( 4 ) 8 ( 12 ) 8 = ( 12 ) 8 ( 4 ) ( 2 ) ( 4 ) = ( 12 ) 8 ( 4 2 ) 4 = ( 12 ) 8 ( 16 ) 4 = 1 2 8 1 6 a 48^8 = ((4)(12))^8=(4)^8(12)^8 = (12)^8(4)^{(2)(4)} = (12)^8(4^2)^4 = (12)^8(16)^4 = 12^816^a

by observation, a = 4

Kamal Banat
Oct 8, 2014

(4^2 X 3)^8 = (4 X 3)^8 X 4^2a, 4^16 X 3^8 = 4^8 X 3^8 X 4^2a, Divide both sides by 3^8, 4^16 = 4^8 X 4^2a, 2a + 8 = 16, a = 4

48^8=12^8x16^a (48/12)^8=16^a 4^8=16^a 4^8=4^2a 8=2a a=4.

Anjali Pal
Oct 7, 2014

2^16 x 12^8=12^8 x 2^4a

2^16==2^4a

4a=16 a=4

Umarali Vp
Oct 7, 2014

48^8 = (12*4)^8 = 12^8 x 16^(1/2)^8 = 12^8 x 16^4

48^8/12^8=16^a 16^a=65536 16^a=16^4 a=4

V Vishnu Prasad
Oct 7, 2014

48^8 = (12*4)^8 = 12^8 x 16^(1/2)^8 = 12^8 x 16^4

Anonymous Person
Oct 7, 2014

Another way to solve it (I think it's one of the more gradual and easier paths to use without calculating the results of the powers):

48^8 = 12^8 * 16^a <=>

<=> (4*12)^8 = 12^8 * 16^a <=>

<=> 12^8 * 4^8 = 12^8 * 16^a <=>

<=> 4^8 = 16^a <=>

<=> 4^8 = (4*4)^a <=>

<=> 4^8 = 4^a * 4^a <=>

<=> 4^8 = (4^a)^2 <=>

<=> 4^4 = (4^a) OR (-4)^4 = (4^a)

In both of those equations, a = 4, so that is the solution.

Yes, I know I could immediately reach the solution after the 5th step, but I wanted to write it slighly different from another solution I saw here.

Anonymous Person - 6 years, 8 months ago

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You should have used L a t e x Latex .

Anuj Shikarkhane - 6 years, 8 months ago
Deepu V.M
Oct 7, 2014

48^8=12^8 16^a (12 4)^8=12^8*16^a (4^2)^4=16^a a=4

48^8 = 12^8 X 16^a = 12 ^8 X 4^2a ---> 2a = 8 --> a =4

Ram Seshadri - 6 years, 8 months ago

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